Verb (dictionary form) + まい / Verb (ます stem) + まい

[Will not / Probably not / Determined not to]

Connection: Verb (dictionary form) + まい (Group 1) / Verb (ます stem) + まい (Group 2/3)

Usage 1 — Negative volitional: Expresses strong determination not to do something.

Usage 2 — Negative conjecture: Expresses the speaker's guess that something probably won't happen.

Key point: Literary/formal expression. する → するまい/すまい, くる → くるまい/こまい

Examples:

二度とあんな失敗はするまいと心に決めた。(I resolved in my heart never to make such a mistake again.)

彼はもう来るまい。(He probably won't come anymore.)

あの人が嘘をつくまい。(That person probably wouldn't lie.)