English uses one word, "can," for two quite different ideas: I can swim because I learned how and I can swim today because the sea is calm. Romanian, like French (savoir vs pouvoir), splits these apart. A ști să expresses acquired competence — a skill you possess, learned and retained: Știu să înot ("I know how to swim"). A putea expresses circumstantial ability or possibility — being able right now, in these conditions. Because English collapses both into "can," English speakers systematically reach for a putea where Romanian wants a ști să, and end up saying the equivalent of "I'm able to swim" when they mean "I know how to swim." Learning to default to a ști să for skills is the single most useful fix this page offers.
a ști + să — acquired skill
To say you know how to do something — a skill you have learned and can perform — use a ști followed by a să-clause. First, the present forms of a ști (irregular):
| Person | a ști (present) |
|---|---|
| eu | știu |
| tu | știi |
| el / ea | știe |
| noi | știm |
| voi | știți |
| ei / ele | știu |
Add a să-clause for the skill itself:
Știu să înot de când eram mic.
I've known how to swim since I was little.
Ea știe să gătească mâncare thailandeză.
She knows how to cook Thai food.
Nu știu să conduc, dar vreau să iau permisul.
I don't know how to drive, but I want to get my license.
The hallmark of a ști să is permanence: the skill exists independently of the moment. That is why Știu să înot needs no "today" or "now" — it is a fact about your abilities, not your present circumstances.
a putea — circumstantial ability and possibility
A putea is about the here and now (or the conditions), not the learned skill. Pot să înot azi means "I'm able to swim today" — the pool is open, my leg has healed, the water is calm. It says nothing about whether I ever learned; it is about present possibility.
Pot să înot azi, apa e liniștită.
I can swim today, the water is calm.
Nu pot să alerg, m-am accidentat la genunchi.
I can't run, I injured my knee.
The contrast becomes vivid when you put the two side by side:
| Romanian | Meaning | What it claims |
|---|---|---|
| Știu să înot. | I know how to swim. | I have the skill (learned it). |
| Pot să înot. | I can swim (now / here). | Conditions allow it right now. |
| Știu să înot, dar azi nu pot. | I know how to swim, but I can't today. | Skill yes, circumstances no. |
Știu să schiez, dar azi nu pot — mi-am uitat schiurile acasă.
I know how to ski, but I can't today — I left my skis at home.
That last sentence is impossible to express cleanly with one English "can," and it is exactly where Romanian's two-verb system shines: știu covers the lasting skill, nu pot covers the momentary obstacle.
a ști + că — factual knowledge
A ști also means "to know (a fact)," and there it takes că ("that") + an indicative clause — not să. This is the knowledge-of-information sense, parallel to English "I know that...".
Știu că vine mâine, mi-a spus chiar el.
I know that he's coming tomorrow, he told me himself.
Știai că muzeul e închis lunea?
Did you know the museum is closed on Mondays?
Nu știam că vorbești și italiană!
I didn't know you also speak Italian!
So a ști branches by what follows it:
- a ști + să
- conjunctiv → a skill ("know how to do"): Știu să dansez.
- a ști + că
- indicative → a fact ("know that"): Știu că dansezi bine.
The verb form after să is non-factual (the skill is a capability, not an event), while the verb after că is factual (a real state of affairs). This mirrors the broader Romanian logic where să marks the unrealized and că reports the real.
Skill, possibility, fact side by side
Știu să cânt la pian.
I know how to play the piano. (skill — a ști să)
Pot să cânt acum, vecinii nu sunt acasă.
I can play now, the neighbors aren't home. (possibility — a putea)
Știu că ai cântat la pian aseară.
I know you played the piano last night. (fact — a ști că)
Common Mistakes
❌ Pot înot.
Incorrect for a skill — and grammatically broken; this neither states a skill nor a clean ability.
✅ Știu să înot.
I know how to swim. (use a ști să for a learned skill)
❌ Pot să vorbesc franceză, am studiat-o zece ani.
Odd — for a learned skill Romanian prefers a ști să.
✅ Știu să vorbesc franceză, am studiat-o zece ani.
I know how to speak French, I studied it for ten years.
❌ Știu să vine mâine.
Incorrect — factual knowledge takes că, not să.
✅ Știu că vine mâine.
I know that he's coming tomorrow.
❌ Tu ști să gătești?
Incorrect — the second person of a ști is știi, with double i.
✅ Tu știi să gătești?
Do you know how to cook?
Key Takeaways
- a ști să = an acquired skill you possess (Știu să înot); a putea = circumstantial ability or permission in the moment (Pot să înot azi).
- English "can" covers both, so consciously switch to a ști să for anything you learned to do.
- a ști + că
- indicative = factual knowledge ("know that"), a different construction entirely.
- Watch the spelling: știu, știi, știe, știm, știți, știu — tu știi has a double i.
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- a putea (can / be able to)A2 — Full present forms of a putea, its unique tolerance of the bare infinitive (pot merge = pot să merg), and how it expresses ability, permission, and possibility.
- a trebui (must / have to)A2 — The invariable modal trebuie for obligation and probability, the past a trebuit să, and the high-value imperfect trebuia să for 'should have / was supposed to'.
- Conjunctiv After Modals: a putea, a trebui, a vreaA2 — How modal and control verbs (a vrea, a putea, a trebui, a încerca, a reuși, a spera) force a să-clause where English uses an infinitive, and the one verb that still tolerates the infinitive.
- Irregular Present: a ști and the 'know' verbsB1 — How to conjugate a ști (to know a fact) and a cunoaște (to know a person or place), and how Romanian splits the single English verb 'know' into two.
- Conjunctiv vs Infinitive: The Balkan ChoiceB1 — When Romanian uses a să-conjunctiv where its Romance cousins use the infinitive, and the handful of constructions where the infinitive survives — the structural signature of Romanian.