Originally it was the length of the furrow in one acre of a ploughed field. An acre is an area that is one furlong long and one chain wide. For this reason, the furlong was once also called an acre's length. Around the year 1300, England standardised the furlong as 40 rods or 660 feet.
Vanilla sex is what a culture regards as standard or conventional sexual behaviour. Different cultures, subcultures and individuals have different ideas about what constitutes this type of sex. Often, it is interpreted as sex which does not involve such elements as BDSM, kink, or fetish activities.
Sexual intercourse (or simply called sex) is the insertion and thrusting of a male's penis into a female's vagina. People and animals that sexually reproduce use sexual intercourse to have an offspring. Sometimes sexual intercourse is called coitus or copulation and is more casually known as having sex or sleeping together. The two animals may be of opposite sexes or they may be hermaphroditic, as is the case with snails. Sexual intercourse may also be between individuals of the same sex.