Putting theory into practice

[MeganN]

I've looked up "infant" in Dyche's Dictionary, which was intended for teaching - it was "peculiarly calculated for the use and improvement of such as are unacquainted with the learned languages". It first appeared in 1735, though my one is a 16th edition of 1777. This says:
INFANT (S.) In Common Speech, means a young child or one under seven years old; but in Law all under twenty-one years are so called.

Seven fits with the idea of stages of life being seven years long, which I've always understood lay behind Shakespeare's seven ages without knowing whose idea it was. It seems to come from the Greeks, but I doubt it was taken seriously later on except for the first three stages of infant, child, and youth (14-21). Even then the terms child and youth were not, by Dyche's day, applied strictly. And didn't it only apply to boys? Was there a female equivalent of "a youth"?

The legal usage of "infant" (at least in the 18th century) is borne out by a 1733 item at TNA found in my own family research:

Reference: C 11/1508/10 Description:
Short title: Bringloe v Scott.
Document type: Bill and answer.
Plaintiffs: Porter Bringloe, Bedell Bringloe, Stafford Bringloe, Capell Bringloe and Edward Bringloe, infants (by John Bringloe, gent of Wood Rising, Norfolk, their father) and said John Bringloe (brother and administrator of Henry Bringloe, mariner deceased).
Defendants: George Scott and William Sawbridge.
Date of bill (or first document): 1733

The "infants" named were born/baptised in 1716, 1717, 1719, 1721 and 1724 respectively. So aged approximately 17, 16, 14, 12, and 9. All boys (no girls in this family then or subsequently) so this doesn't speak to the gender query.

The father, John Bringloe, was my direct ancestor. Sorry Peter, he isn't in my LC list because he didn't make it to the 1841 Census, let alone 1881. Nor did the sons but some of their progeny did. And they are definitely there!