turn into, become, get, grow, elapse, reach
成 centers on a process of change leading to a result: turning into something, becoming, growing, or reaching a state. The idea of elapsing also fits as time passing until a point is reached.
to become; to get; to grow; to turn; to reach; to attain
success; achievement
completion; perfection; accomplishment
Heisei era (1989.1.8-2019.4.30)
growth; development; growing up; becoming an adult
I see; that's right; indeed
composition; construction; formation; makeup; structure; organization; organisation
making (a report, plan, contract, etc.); drawing up; writing out; preparing; creating (a file, website, account, etc.)
achievement; attainment; accomplishment; realization
rearing; training; nurture; cultivation; promotion
formation; establishment; materialization; coming into existence
(good) result; outcome; fruits (of one's labors); product; accomplishment
formation; molding; making (up); taking form; giving form to
adult; grown-up
approval; agreement; support; favour; favor
ingredient; component; composition
results; record; grades; marks
composition; formation; organization; organisation; compilation
composition; synthesis; compounding; combining
as (much) as possible; as (much) as one can; wherever practicable; if possible
creation; generation; formation; derivation
formation; combination
to form; to make; to constitute
minority (i.e. being under age); minor; underage person
成 is thought to combine 戊 (a halberd-like weapon) with 丁 (a nail or small stroke), suggesting the idea of completing or finishing something, perhaps originally related to a ritual or action. The exact historical development is uncertain.
The outer shape 戊 looks like a container, and the inner stroke 丁 is like a seed sprouting. Picture something inside a vessel growing and turning into its final form.
For セイ, imagine a seed growing into a plant and you say, 'Say, it became a tree!' The word 'say' cues セイ while the seed reaches its final form.