Rules for writers, Tenth edition - Diana Hacker, Nancy Sommers 2021

Use a semicolon between closely related independent clauses not joined with a coordinating conjunction
The semicolon
Punctuation

The semicolon is used to connect major sentence elements of equal grammatical rank. When two independent clauses appear in one sentence, they are usually linked with a comma and a coordinating conjunction (and, but, or, nor, for, so, yet). If the clauses are closely related and the relation is clear without a conjunction, they may be linked with a semicolon instead.

In film, a low-angle shot makes the subject look powerful; a high-angle shot does just the opposite.

A semicolon must be used whenever a coordinating conjunction has been omitted between independent clauses. To use merely a comma creates a type of run-on sentence known as a comma splice. (See 20.)