Reproductive organ in the context of Chara (alga)

The stamen (pl.: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium.

Estradiol (E2), also called oestrogen, oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of female reproductive cycles such as estrous and menstrual cycles. Estradiol is responsible for the development of female secondary sexual characteristics such as the breasts, widening of the hips and a female pattern of fat distribution. It is also important in the development and maintenance of female reproductive tissues such as the mammary glands, uterus and vagina during puberty, adulthood and pregnancy. It also has important effects in many other tissues including bone, fat, skin, liver, and the brain.

In biology, trimorphism is the existence in certain plants and animals of three distinct forms, especially in connection with the reproductive organs.

In trimorphic plants there are three forms, differing in the lengths of their pistils and stamens, in size and color of their pollen grains, and in some other respects; and, as in each of the three forms there are two sets of stamens, the three forms possess altogether six sets of stamens and three kinds of pistils. These organs are so proportioned in length to each other that half the stamens in two of the forms stand on a level with the stigma of the third form. To obtain full fertility with these plants, it is necessary that the stigma of the one should be fertilized by pollen taken from the stamens of corresponding height in another form. Hence six unions are legitimate, that is, fully fertile, and 12 are illegitimate, or more or less unfertile. Wallace has shown that the females of certain butterflies from the Malay Archipelago appear in three conspicuously distinct forms without intermediate links.

Sexual activity, sexual practice, sexual behaviour or very broadly sex is the set of activities people engage in that typically includes any combination of physical intimacy, physical contact with the reproductive organs (genitals) or erogenous zones, and erotic stimulation. Sexual acts range from activities done alone (e.g., masturbation) to acts with another person (e.g., sexual intercourse, non-penetrative sex, oral sex, etc.) or multiple persons (e.g., orgies) in varying patterns of frequency, for a wide variety of reasons. Sexual activity usually results in sexual arousal and physiological changes in the aroused persons, some of which are pronounced while others are more subtle. Certain conduct is intended to arouse the sexual interest of another or enhance one's already-existing sex life with another or between individuals (for instance, foreplay or BDSM).

Certain activities, such as strategies to find or attract partners (flirting, courtship and display behaviour), are not usually considered sex, though they are commonly used to lead to sexual arousal and more explicitly sexual activities.