Translative, Terminative, Essive, Comitative, Abessive

Translative

to become who? to become what?
The translative is formed from the genitive stem by adding the case ending -ks.
õhtu, õhtu, õhtut > õhtuks
kokk, koka, kokka > kokaks

The translative is used:
1) to express becoming somebody, turning into something, e.g. Ta saab arstiks. \He will be a doctor.\
2) to express a period of time, e.g. Tule suveks meile. \Come to our place for the summer.\
3) to express a temporal limit, e.g. Too raamat homseks. \Bring the book by tomorrow.\

Verbs governing the translative: muutuma, saama, valmistuma, etc.
E.g. Ta valmistus eksamiks.

Terminative

up to who? up to what?
The terminative is formed from the genitive stem by adding the case ending -ni.
jõgi, jõe, jõge > jõeni

The terminative is used:
1) to express a spatial limit, e.g. Mine nurgani ja keera vasakule. \Go to the corner and turn left.\
2) to express a temporal limit, e.g. Kauplus on avatud kümnest kuueni. \The shop is opened from ten to six.\

Essive

as who? as what?
The essive is formed from the genitive stem by adding the case ending -na.
autojuht, autojuhi, autojuhti > autojuhina

The essive is used to express a function, a feature, e.g. Ta töötab koolis õpetajana. \She works as a teacher in the school.\ 

Abessive

without whom? without what?
The abessive is formed from the genitive stem by adding the case ending -ta.
raha, raha, raha > rahata

The abessive is used to express lack of something.
E.g. Rahata ei saa maja osta. \One cannot buy a house without money./

Comitative

with whom? with what?
The comitative is formed from the genitive stem by adding the case ending -ga.
tütar, tütre, tütart > tütrega

The comitative is used:
1) to express means of action, e.g. Ta läheb koju rongiga. \He goes home by train.\
2) to express accompanying, e.g. Te lähete koos sõbraga kinno. \You are going to cinema with your friend.\
3) to indicate a period of time, e.g. Ma lõpetan töö kolme päevaga. \I finish the work in three days.\

Verbs governing the comitative: abielluma, kohtuma, konsulteerima, pahandama, rääkima, suhtlema, sõbrustama, tegelema, tutvuma, hüvasti jätma, juttu ajama, rahul olema, toime tulema, etc.
E.g. Sõber tegeleb spordiga. Peeter abiellub Tiiuga.