[Vた] り [Vた] り する
When you list a couple of things you did — but you're not trying to give a complete or ordered account — Japanese uses the 〜たり pattern. きのう、本 を 読んだり、テレビ を 見たり しました。 = 'Yesterday I read a book, watched TV, (and so on).' The implication: those are examples of what I did, not the full list. The form is built on the plain past (〜た) you already know — just swap the final た for たり — and the whole thing is closed with a form of する that carries the tense for the whole sentence.
How to build 〜たり
Take the plain past form (〜た / 〜だ) and add り. たべた → たべたり. のんだ → のんだり. 行った → 行ったり. 見た → 見たり. した → したり. 来た → 来たり. The voicing follows the past form — if the past is 〜だ (like のんだ), the たり version is 〜だり (のんだり). If you can build 〜た, you can build 〜たり — the rule is identical.
The full pattern: …たり、…たり する
Two 〜たり clauses, then close with する in whatever tense you want: する (do — present / habitual), しました (did — past), して います (am doing — ongoing). しゅうまつ は、本 を 読んだり、えいが を 見たり します。 = 'On weekends I (sometimes) read books and watch movies.' きのう、ともだち と あったり、カフェ に 行ったり しました。 = 'Yesterday I met up with friends, went to a café, (and other things).' Listing two actions is the standard — listing one feels incomplete; three is fine but less common.
Why not just 〜て?
〜て chains actions in sequence: 本 を 読んで、テレビ を 見ました。 = 'I read a book and (then) watched TV' — implying that order, and that those two things were what I did. 〜たり is non-sequential and non-exhaustive: 'I read books, watched TV, and stuff like that'. If you want to say 'I did A then B and that's the full story', use 〜て. If you want to say 'I did things like A and B', use 〜たり. English doesn't distinguish these crisply, but Japanese does.
Adjectives and nouns with 〜たり
い-adjectives: past form (〜かった) + り = 〜かったり. てんき は、あつかったり、さむかったり します。 = 'The weather is hot some days, cold others.' な-adjectives and nouns: past plain (〜だった) + り = 〜だったり. やすみ だったり、しごと だったり します。 = '(Some days are) days off, (some are) work days.' Used to express variation or alternation, especially with weather, mood, or schedule. The closing する is still required.
Negative — 〜なかったり
Plain past-negative (〜なかった) + り = 〜なかったり. 食べたり、食べなかったり します。 = 'Sometimes I eat (it), sometimes I don't.' This pattern leans on the alternation reading — to express that something happens inconsistently. 来たり、来なかったり します。 = '(They) come some days, don't come other days.' For most learners, this is a one-step extension of the basic pattern — same logic, the 〜なかった just plugs into the same +り slot.
Common pitfalls
Don't forget the closing する: 読んだり、見たり しました — without the しました, it sounds unfinished. Don't use 〜たり for every list — it's specifically the non-exhaustive, example-giving list. For 'I went to the bank, then the post office, then home', stick with 〜て: ぎんこう に 行って、ゆうびんきょく に 行って、うち に かえりました. 〜たり would imply 'I went to the bank, the post office, (and other places).' One-clause 〜たり is grammatical but sounds incomplete; default to two.
