Russian / Verb Morphology

The particle ся

A worn-down "self" that hooks onto the end of a verb, after every other ending, and quietly changes what the verb does. Tap any speaker to hear it.

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Where it comes from
себя becomes ся / сь
"oneself" collapsed into a particle stuck on the verb

It is a postfix: it lands after the personal ending, not before it. You conjugate the verb completely as normal, then tack ся on the very end.

сяafter a consonant or ь
учится, учишься
сьafter a vowel
учусь, учитесь
Conjugation: учиться

to study, to be a student

яучусь
тыучишься
он / онаучится
мыучимся
выучитесь
ониучатся
Watch the particle flip: учусь and учитесь take сь because a vowel sits in front. Everything else takes ся.
учить versus учиться

Adding the particle does not just mean "teach yourself." It swaps a verb that takes an object for one that cannot.

учить
to teach, or to study something specific (takes a direct object)
Она учит русский.
She is studying Russian.
учиться
to learn, to be a student (no object)
Она учится в университете.
She studies at the university.
The most useful pattern in the language: ся takes a transitive verb (one that acts on an object) and makes it intransitive (no object). Learn that flip and most reflexive verbs stop being mysterious.
Spelling: учится versus учиться

One soft sign separates the infinitive from the conjugated form, and Russian gives you a built-in test.

учиться
to study (infinitive)
answers что делать?
the question has a ь, so the verb does too
учится
he / she studies (3rd person)
answers что делает?
no ь in the question, none in the verb
Quick test: if English would use "to" (the infinitive), keep the ь. It hides in front of the particle: учиться.
The five jobs of ся
01True reflexive

The action loops back onto the subject. The literal "self" meaning.

Он моет машину.He washes the car.
Он моется.He washes (himself).
02Only exists with the particle

Some verbs never appear without it. Nothing to "undo," just learn them whole.

улыбатьсяto smile
смеятьсяto laugh
боятьсяto be afraid
надеятьсяto hope
03Transitive to intransitive

The workhorse. Turns "do X to something" into "be in the state of X." This is учиться.

Я учу слова.I'm learning words.
Я учусь.I'm studying / a student.
04Passive

Something has the action done to it. Common in writing.

Дом строится.The house is being built.
Книга читается легко.The book reads easily.
05Reciprocal ("each other")

Two or more subjects act on one another.

Они встречаются.They meet / are dating.
Они целуются.They kiss (each other).
The only other postfixes

True postfixes (particles glued after the ending) are rare. This is essentially the whole set, so nothing else of this kind will ambush you.

ся / сьreflexive, the one on this page
тоspecific but unknownкто-то = someone
нибудьany one will doчто-нибудь = something
либоanyone at all (bookish)кто-либо = anyone
каsoftens a commandдай-ка = go on, give it here
The verbs that change meaning constantly are built with prefixes (about 20 of them) and derivational suffixes (many). Those you meet word by word in context, never as a list.
One thing to remember

You do not need any of this to start speaking. Я учусь already says "I'm studying," and you can say true things today with present tense and a handful of verbs. Grammar is cleanup after you have already been wrong out loud. Meet ся in the wild, then come back to this page.