Conjugation

〜ます / 〜ません

Polite present / negative

Use in formal conversation, with strangers, teachers, or anyone you want to show respect to. Most daily speech uses this form.

〜ました / 〜ませんでした

Polite past / negative past

Same politeness as ます but for completed actions. 昨日食べました = I ate yesterday.

〜て form

Connector / request

Most versatile form. Connects actions, makes requests (〜てください), expresses ongoing actions (〜ています), and many grammar patterns.

〜ない form

Plain negative

Casual "do not." Base for: 〜ないでください, 〜なければなりません, 〜なくてもいい.

〜た form

Plain past

Casual past. Also used in: 〜たことがあります (have done), 〜たら (when/if), 〜たあとで (after doing).

Verb groups

G1 (U-verbs) — ends in う sound. て form follows a chart (く→いて, ぐ→いで, す→して…).
G2 (Ru-verbs) — ends in る, preceded by え/い sound. Drop る, add ending.
G3 — only する and くる. Fully irregular, must memorise.