correct, justice, righteous, 10**40
正 centers on correctness and moral rightness: being correct, just, or righteous. The large-number sense (10**40) is a separate specialized usage.
right; correct
honest; frank; candid; straightforward
exactly; just; precisely; really; truly; surely; certainly; without doubt
amendment; correction; revision; modification; alteration; retouching; update; fix
accurate; correct; precise; exact
justice; right; righteousness
revision; amendment; alteration
(logical) true; regular
correct answer; right solution; correct interpretation
regular; normal; formal; legal; established; legitimate
injustice; unfairness; wrongdoing; iniquity; impropriety; irregularity; dishonesty; illegality; fraud
true character; true form; true colors; identity; truth (of a mystery, phenomenon, etc.); origin
formal; official; regular; proper; legal; due (formalities)
normal; regular
just; justifiable; right; due; proper; equitable; reasonable; legitimate; legal; lawful
front; frontage; facade; main
New Year (esp. first three days)
justice; fairness; impartiality
Taishō era (1912.7.30-1926.12.25); Taisho era
correction; revision; amendment
reasonable; suitable
correction; revision; compensation (e.g. to a pendulum)
correction (of a fault, defect, flaw, etc.); remedy; rectification; redress; reform; straightening (of teeth)
to correct; to rectify; to reform; to amend; to redress
正 is traditionally explained as 一 (one) over 止 (stop), suggesting a single straight line that stops deviation, hence correctness. The exact historical development is uncertain, but the component explanation is widely used.
The top line 一 acts as a straight edge, and the bottom 止 stops any crookedness. Together they make everything correct and just.
For セイ, imagine a judge saying 'say' the correct verdict: say -> セイ, and the gavel stops all wrong arguments.