Abnormal temperature: A basal body temperature among the pre-shift six, or within the thermal shift, that is clearly out of the range of the surrounding temperatures. 

Abortion: The deliberate termination of a newly conceived life. Not to be confused with spontaneous abortion (miscarriage). 

Abortifacient: A drug or device used to cause an abortion. 

Abstinence: The practice of refraining from indulging an appetite or desire, e.g., marital relations. 

Amenorrhea: Lack of menstrual periods. 

Anovulatory cycle: A menstrual cycle without ovulation. 

Basal body temperature: The temperature of the human body at rest or upon awakening, unaffected by food, drink or activity. 

Blastocyst: The beginning stage of new life immediately after conception, when the cells begin to divide and grow. 

Breakthrough bleeding: A bleeding episode that is not part of menstruation. It can appear as spotting or days of bleeding in the middle of a cycle, and it can also occur as a regular period following an anovulatory cycle. Breakthrough bleeding can mask the presence of mucus, and it can be a potentially fertile time. 

Breastfeeding, continued: Nursing beyond six months when the introduction of other foods and liquids are added to complement the breast milk. 

Breastfeeding, exclusive: The standard of care for babies during their first six months of life, characterized by nursing whenever the baby indicates a desire (day or night), with each feeding fully emp- tying the breast of milk. 

Breastfeeding, mixed: High mixed: 80% of the feeding comes from the breast; medium mixed: 20–79% of the feeding comes from the breast; low mixed: less than 20% of the feeding comes from the breast. 

Calendar Rhythm: The 1930s forerunner of modern NFP based on an assumption that ovulation occurred around Cycle Day 14. It took into account a woman’s past cycle history, but did not take into account any activity occurring during the current cycle. 

Cervical mucus: A natural fluid of the body that is necessary for the proper functioning of a woman’s reproductive system and is an aid to fertility. 

Cervical os: The opening of the cervix. 

Cervix: The lower, narrow part of the uterus that extends slightly into the vagina; the opening to the uterus. 

Clitoris: A part of the female genitalia consisting of a small elongated highly sensitive erectile organ at the front of the vulva. 

Coitus: A Latin term for sexual intercourse. 

Conception: The union of one male sperm and one female ovum; the beginning of a new human life. Also called fertilization. 

Condom: A sheath made of thin rubber or latex, to cover the penis as a contraceptive during sexual intercourse. 

Contraception: The use of mechanical, chemical or medical procedures to prevent conception resulting from sexual intercourse. Not to be confused with responsible parenthood. 

Corpus luteum: A yellow, progesterone-secreting structure that forms from an ovarian follicle after the release of a mature egg. If the egg is not fertilized, the corpus luteum secretes progesterone for approximately 14 days after ovulation. 

Diaphragm: A contraceptive device consisting of a flexible disk that covers the cervix. 

Ejaculation: The spasmodic expulsion of semen from the penis. 

Embryo: The stage of human life from implantation through the eighth week of development. 

Endometrium: The inner lining of the uterus. 

Epididymis: The comma-shaped male sexual organ attached to the top and to the back of the testicles that assists in the storage and maturation of the sperm. 

Estrogen: A fertility hormone that causes the cervix to undergo physical changes and to secrete mucus, and which causes the development of the endometrium. 

Estimated Date of Childbirth: See Naegele Rule and Prem Rule. 

Fallopian tubes: The pair of tubes that transport female eggs from either ovary to the uterus. 

Fertile time: The time of a woman’s menstrual cycle leading up to and including the time of ovulation, characterized, in part, by the presence of mucus. Sexual intercourse during this time (Phase II) could result in conception. 

Fertility: The quality or condition of being able to produce offspring. 

Fertility awareness: Use of physical signs and symptoms that change with hormonal fluctuations throughout a woman’s menstrual cycle to predict a woman’s fertility. 

Fertility monitor: A device that measures hormone levels, such as estrogen or luteinizing hormone (LH), to detect the fertile time of a woman’s cycle. 

Fertilization: The union of one male sperm and one female ovum; the beginning of a new human life. Also called conception. 

Fetus: The stage of life development beginning at eight weeks after implantation and continuing until birth. 

Follicle: One of thousands of small ovarian sacs containing an immature ovum; each cycle, one follicle fully matures and is released at ovulation. Upon release of its egg, the follicle becomes a structure called the corpus luteum. 

Follicle Stimulating Hormone (FSH): A fertility hormone secreted by the pituitary gland to stimulate the maturation of ovarian follicles. 

Formula feeding: A baby is fed with a bottle and receives only formula (no breast milk). 

Hormonal contraception: Any drug, device, or implant that utilizes synthetic hormones to alter fertility in an effort to disrupt the natural process of conception. 

Hormone: A chemical substance produced by a gland or organ of the body and carried by circulation to other areas where it produces an effect. 

Human Chorionic Gonadotropin (hCG) hormone: A hormone produced by the placenta that maintains the corpus luteum and stimulates it to continue producing progesterone for the first 10–12 weeks of pregnancy. 

Implantation: The process of an embryo attaching to the lining of the uterus. 

Infertile time: The time of a woman’s menstrual cycle both before the ovulation process begins as well as after ovulation, characterized, in part, by the absence of mucus. Sexual intercourse during these times (Phases I and III) does not result in conception. 

Infertility: The quality or condition of being unable to produce offspring. 

Injectable hormonal contraceptives: A liquid artificial hormone that is injected into a woman’s body with a needle (a shot). Examples include Depo-Provera and Lunelle. 

Intrauterine device (IUD): A metal or plastic loop, ring, or spiral inserted into the uterus to prevent conception; acts as an abortifacient by preventing the implantation of a newly conceived life. 

In vitro fertilization: A specialized technique by which an ovum is fertilized by sperm outside the body, with the resulting embryo later implanted in the uterus. 

Labia: The inner and outer lips of the vulva; the outermost parts of the female genital sex organs. 

Libido: Feelings of sexual desire. 

Luteal phase: A stage of the menstrual cycle, lasting about two weeks, measured by counting the days from the first day of temperature rise to the last day of the cycle. 

Luteinizing hormone (LH): A fertility hormone produced by the pituitary gland that helps to stimulate ovulation in females. 

Menarche: The first menstrual period; the establishment of menstration. 

Menopause: The period marked by the natural and permanent cessation of menstruation; officially reached after 12 months of no menstrual periods. 

Menstruation: The periodic discharge of blood and tissue from the uterus in non-pregnant women from menarche to menopause (following a sustained thermal shift). 

Method effectiveness: The effectiveness of a method intended to deploy/postpone pregnancy assuming perfect use; when calculating, it includes only those unintended pregnancies that resulted from correct and consistent use of the method.

Missed temperature: A basal body temperature that is not recorded on a woman’s menstrual cycle chart on a given day.  

Mucus characteristics: The qualities of mucus that a woman sees and/or touches when making observations. 

Mucus-Only Methods: Methods of natural family planning based on reading and interpreting the cervical mucus of a woman’s menstrual cycle. 

Mucus sensations: The qualities of mucus that a woman feels and senses throughout the day and when wiping at bathroom visits. 

Naegele Rule: A rule traditionally used by the medical community to calculate the Estimated Date of Childbirth (EDC); calculated by adding seven days to the first day of the last menstrual period, and then adding nine months. 

Natural Family Planning (NFP): A means of reading a woman’s signs of fertility and infertility; also known as fertility awareness. 

Non-Injectable hormonal contraceptives: All forms of birth control that introduce artificial hormones into a woman’s body in ways other than injection (e.g., pills, patches, ring, etc.). 

Ovary: The female reproductive organ containing the ova, or eggs. 

Ovulation: The process of an ovarian follicle releasing its ovum, thus making a woman fertile and able to become pregnant. 

Ovum: The female reproductive cell, or egg; plural: ova. 

Oxytocin: A hormone released from the pituitary gland that stimulates the contraction of the smooth muscle of the uterus during labor and facilitates release of milk during nursing; called the “hormone of love.” 

Penis: The male external sexual organ. 

Perimenopause: The last two to eight years of the premenopause transition, ending one year after a woman’s last menstrual period. 

Pituitary gland: A gland located at the base of the brain that releases various hormones that control the functions of other organs. 

Postpartum: Of or occurring in the period of time after childbirth; after delivery. 

Premenopause: The natural life progression that occurs as a woman’s fertile years gradually come to a close. It can begin as early as age 35, although the average age at the start of premenopause is 45. Often referred to by the medical community as perimenopause. 

Progesterone: A fertility hormone secreted by the corpus luteum that causes a woman’s temperature to rise, prepares the uterus for the fertilized ovum, and helps sustain a pregnancy. 

Prolactin: A pituitary hormone that stimulates and maintains the secretion of milk; referred to as “the mothering hormone.” Higher levels of prolactin during breastfeeding play a role in the delay of ovulation. 

Prostate gland: The male sexual organ that controls the release of urine from the bladder and provides a fluid to assist in the transport of sperm. 

Puberty: The stage of adolescence in which an individual becomes physiologically capable of reproduction. 

Responsible parenthood: The intentional decisions by a married couple to plan or to postpone conception through the knowledge and practice of fertility awareness. Not to be confused with contraception. 

Scrotum: The sac below the penis that contains the testicles. 

Semen: The fluid that is released through the penis during orgasm. Semen is made up of secretions of the reproductive glands and sperm. 

Seminal fluid: A fluid produced by the seminal vesicles that assists in the transport of the sperm, and is expelled through the end of the penis when a man achieves sexual climax. 

Seminal vesicles: Sac-like pouches in the male that attach to the vas deferens and produce a sugar-rich fluid (fructose) that provides sperm with a source of energy and helps with the sperm’s ability to move. 

Sperm: Male reproductive cells made by the testicles. 

Spermicide: A sperm-killing agent, most often a cream or jelly, usually used as a contraceptive. 

Sterilization: The process of rendering either male or female sterile or infertile. 

Sympto-Thermal Method (STM): A method of fertility awareness that utilizes the observation of changes in the cervical mucus and basal body temperature to determine the fertile and infertile times of a woman’s menstrual cycle. 

Testicles (or testes): The male sexual organs that are contained in the scrotum and produce sperm. 

Tubal ligation: A method of female sterilization in which the Fallopian tubes are surgically tied, cut or cauterized. 

Unintended pregnancy rate: Measured in terms of the number of women out of 100 who become pregnant in one year using a method intended to delay/postpone pregnancy. 

User effectiveness: The effectiveness of a method intended to postpone/delay pregnancy based on actual practice; when calculating, all unintended pregnancies occurring during a study and all months or cycles are included, whether the method or rules were followed correctly or incorrectly. 

Uterus: A hollow, pear-shaped organ in which a baby grows during the nine months of pregnancy; frequently called the womb. 

Vagina: The female genital canal extending from the uterus to the vulva. 

Vaginal sponge: A sponge that combines barrier and spermicidal methods of contraception, inserted vaginally prior to intercourse over the cervix to prevent conception. 

Vas deferens: A narrow, muscular tube that connects the testicles to the urethra in the penis through which the sperm flow. 

Vasectomy: Surgical excision of a part of the vas deferens, used as a method of male sterilization. 

Vulva: The external parts of the vagina, including the labia. 

Withdrawal: As a method of contraception, the act of removing the penis from a woman’s vagina prior to ejaculation; also known as coitus interruptus. 

Withdrawal bleed: The bleed that occurs monthly while using non-injectable hormonal contraceptives.