The plain past form is the casual past tense. It is used in informal speech and in many grammar patterns. It corresponds to ました in polite speech. Key points: • Plain past is casual: 行った, 食べた, 見た • Used with friends/family or in diaries • Also appears before grammar like 〜と思う (later) • Time words show when it happened For example, “昨日行った” means “I went yesterday.” “本を読んだ” means “I read a book.” The plain past form changes depending on verb group, so you must learn common forms. Ru-verbs drop る and add た (食べる → 食べた). U-verbs change endings (書く → 書いた, 読む → 読んだ). Irregular verbs are する → した, 来る → 来た. Even if you mostly speak politely, you will see these forms in conversation, anime, and casual messages. Recognizing them helps you understand native speech. At N5, focus on a few common verbs and their past forms. This builds a strong base for casual Japanese.