Questions & Answers about Иногда я улыбаюсь просто так.
The infinitive is улыбаться.
- улыбаться = to smile (an ongoing or habitual action).
- улыбаюсь = I smile / I am smiling (1st person singular, present tense, imperfective).
So Иногда я улыбаюсь просто так literally is “Sometimes I smile just because.”
The ending -юсь contains two things:
- -ю → 1st person singular present (I …).
- -сь → reflexive marker (a reduced form of -ся).
Historically, reflexive -ся / -сь can mean “to do something to oneself,” but with many verbs (including улыбаться) it has become a fixed part of the verb and no longer feels like “myself” to native speakers.
So:
- улыбаюсь is just how you say “I smile” in Russian.
- There is no separate non‑reflexive everyday verb for “to smile” (улыбать is not used in the same sense). The reflexive form is simply the normal verb.