The answer is YOUTH, five letters. English has used youth for a single young person since around 1200, and it is the most neutral word in this field, covering the years between childhood and adulthood without naming an exact age. CHILD shares the five-letter slot, TEEN takes four and KID takes three.
YOUTH and CHILD never share a square
The five-letter pair looks like a coin flip, but it is the easiest split in the whole field. Write the two words one above the other and no square matches: Y against C, O against H, U against I, T against L, H against D. Any single crossing, wherever it lands, leaves only one of them standing.
Meaning points the same way before you have crossings. CHILD usually means someone below the teenage years. YOUTH starts roughly where childhood ends and runs until adulthood, and it has a second job as a mass noun, as in the energy of youth, which is actually the older of the two senses. Old English geoguð meant youthfulness and young people collectively; the single young person came later, by about 1200.

The teen words arrived in an odd order
You might expect TEENAGER to be the original and TEEN to be the clipped version. The dates say otherwise. Teen as a noun for a teenaged person is recorded from 1818, though it was rarely used before the 20th century. TEENER, an American word for a teenager, turns up from 1894. The adjective teenage followed in 1911, first in reference to Sunday school classes, and TEENAGER itself does not appear until 1922.
That history is why grids still carry TEENER, six letters, the older word that teenager followed. Newsday has clued TEENER as Young person. When a six-square slot refuses every obvious candidate, try it before you start doubting your crossings.
KID started out on the farm
KID, three letters, began as the word for a young goat, borrowed from a Scandinavian source around 1200. The sense of a child appears perhaps by the 1590s, certainly by the 1680s, and only settled into common informal use after the 1840s. The goat never fully left: kid gloves were gloves made of kidskin leather by the 1670s, and the figurative sense of handling someone delicately is recorded by 1913.
SPRINGCHICKEN, the thirteen-letter answer, is the other farmyard entry. Dictionaries still list its poultry sense first, a young chicken, especially a broiler or fryer, and the person sense second. In everyday speech it mostly turns up in the idiom no spring chicken, which makes it a slightly cheeky fill for a clue that simply asks for a young person. Newsday has used it that way.
Young person fills, three squares to thirteen
Match the tone of the clue as well as the square count:
| Letters | Answer | Register |
|---|---|---|
| 3 | KID | Informal, the everyday word |
| 3 | TAD | A small child, usually a boy |
| 4 | TEEN | Thirteen to nineteen |
| 5 | YOUTH | Neutral, no fixed age |
| 5 | CHILD | Before the teenage years |
| 6 | TEENER | Older American word for a teenager |
| 8 | JUVENILE | Legal or scientific tone |
| 8 | TEENAGER | The full modern form |
| 10 | ADOLESCENT | Formal or clinical tone |
| 13 | SPRINGCHICKEN | The idiom, run together |
Adolescent and adult come from one Latin verb
The two formal fills are closer than they look. Latin adolescere meant to grow up or come to maturity. ADOLESCENT comes from its present participle, so it describes someone still growing up, while adult comes from the past participle adultus, someone who has finished. English took adolescent in the mid-15th century and adult in the 1530s.
JUVENILE has a different Latin source, iuvenis, a young man. The adjective reached English in the 1620s, and the noun for a young person followed by 1733. It is also a distant cousin of YOUTH: both go back to the same ancient Indo-European root for vital force and youthful vigor, the root behind young and junior as well. JUVENILE and TEENAGER both fill eight squares, and like YOUTH and CHILD they line up without a single matching square, so any crossing picks one.