长 (zhǎng) — long (in space or in time)

Meanings

long (in space or in time)
Long — of an object, a piece of clothing, or a stretch of time. As a predicate it takes a degree adverb like any Chinese adjective: 这件衣服很长.
adjective
to grow, to grow up
The same character as 长 cháng "long", read zhǎng and meaning something quite different: to increase in size or in years. 长大 to grow up, 长高 to grow taller. The reading is the word — HSK 3 lists 长 a second time for exactly this reason.
verb
长得… — to look, to be built (a certain way)
verb
Appearance is described with 长得 plus a comment: 长得很高, 长得像妈妈, 长得很漂亮. Chinese frames looks as the result of growing, which is why the verb of growth carries them.

长長
cháng (second tone, rising) zhǎng (third tone, dipping)
(cháng) long; length; (zhǎng) to grow, to develop; elder, senior; the head of an organisation
4 strokesRadical 長
长長
cháng (second tone, rising) zhǎng (third tone, dipping)
(cháng) long; length; (zhǎng) to grow, to develop; elder, senior; the head of an organisation
4 strokesRadical 長

这件衣服太长了。這件衣服太長了。Zhè (fourth tone, falling) jiàn (fourth tone, falling) yīfu (first tone, high and level) tài (fourth tone, falling) cháng (second tone, rising) le. (neutral tone)···
This piece of clothing is too long.
这个孩子长得很快。這個孩子長得很快。Zhège (fourth tone, falling) háizi (second tone, rising) zhǎng (third tone, dipping) de (neutral tone) hěn (third tone, dipping) kuài. (fourth tone, falling)···
This child is growing fast.
今天考试的时间很长。今天考試的時間很長。Jīntiān (first tone, high and level) kǎoshì (third tone, dipping) de (neutral tone) shíjiān (second tone, rising) hěn (third tone, dipping) cháng. (second tone, rising)···
Today’s exam went on a long time.
她长得很像她妈妈。她長得很像她媽媽。Tā (first tone, high and level) zhǎng (third tone, dipping) de (neutral tone) hěn (third tone, dipping) xiàng (fourth tone, falling) tā (first tone, high and level) māma. (first tone, high and level)···
She looks very like her mother.

Not quite这个孩子很长。
Correct这个孩子长得很高。
Read cháng, 长 means "long" and describes roads and hair, not the growth of a child. Growth needs the zhǎng reading and the 得 that carries the comment: 长得很高.