Liseyi geçen yıl bitirdim.

Because liseyi is the definite direct object form of lise (high school).

• lise = high school
• liseyi = the high school / high school (as a specific thing being finished)

The ending -(y)i is the accusative ending. The y appears as a buffer consonant because lise already ends in a vowel.

So:

• lise
  • -(y)i → liseyi

In this sentence, the school is the thing being completed, so Turkish uses the accusative.

Bitirdim means I finished.

It comes from the verb bitirmek = to finish, to complete.

Breakdown:

• bitir- = verb stem
• -di = past tense
• -m = I

So bitirdim = I finished.

Yes, this is a very common learner question.

In Turkish, liseyi bitirmek literally means to finish high school, but in natural English this is often translated as to graduate from high school.

So depending on context:

• Liseyi geçen yıl bitirdim. = I finished high school last year. = I graduated from high school last year.

Both can be good translations.

Geçen yıl means last year.

Literally:

• geçen = passing / the one that passed
• yıl = year

So it is something like the year that passed, which Turkish uses to mean last year.

Because Turkish often leaves out the subject pronoun when it is already clear from the verb ending.

Here, bitirdim already shows I because of -m.

So:

• bitirdim = I finished
• ben bitirdim = I finished

The pronoun ben is optional here. It is usually added only for emphasis or contrast.

The most neutral word order here is:

• Liseyi geçen yıl bitirdim.

Turkish often puts the verb at the end, so this is very natural.

But Turkish word order is somewhat flexible. For example:

• Geçen yıl liseyi bitirdim.

This also means I finished high school last year.

The difference is mainly in emphasis:

• Liseyi geçen yıl bitirdim may slightly highlight high school
• Geçen yıl liseyi bitirdim may slightly highlight last year

Yes, absolutely.

• Liseyi bitirdim = I finished high school
• Liseden mezun oldum = I graduated from high school

Both are natural, but they are not identical in structure:

• liseyi bitirmek focuses on finishing/completing school
• liseden mezun olmak specifically means to graduate from high school

So if you want the most exact equivalent of graduate, mezun olmak is often the better choice.

The past tense in Turkish has four common forms:

• -dı
• -di
• -du
• -dü

The vowel changes because of vowel harmony.

In bitirdim, the stem contains the vowel i, so the past tense appears as -di.

Then the I ending -m is added:

• bitir-di-m

So the form matches Turkish vowel harmony rules.

Because Turkish expresses that idea differently.

English uses:

• last year

Turkish uses:

• geçen yıl

Here, geçen does the job of last in this time expression. So you do not need a separate word that matches English word-for-word.

This is a good example of why direct word-for-word translation is often not the best way to understand Turkish.

Yes, liseyi is definite, but Turkish does not use articles like a/an/the the way English does.

Instead, Turkish often shows definiteness through grammar, especially with the accusative ending.

So in this sentence, liseyi is understood as a specific school level or institution being completed. In natural English, we usually just say:

• I finished high school last year
• I graduated from high school last year

Even though English normally likes articles, with school/high school/college in some expressions, English often leaves them out too.

A simple guide:

• geçen ≈ GEH-chen
• bitirdim ≈ bee-teer-DEEM
• liseyi ≈ lee-seh-YEE

A few useful points:

• ç is pronounced like ch
• c in Turkish is pronounced like English j
• i is usually like ee in see
• Stress in Turkish often falls near the end, but natural sentence rhythm matters too

So the whole sentence sounds roughly like:

• lee-seh-YEE GEH-chen yuhl bee-teer-DEEM

The same pattern works with many nouns.

For example:

• Üniversiteyi geçen yıl bitirdim. = I finished university last year.
• Okulu geçen yıl bitirdim. = I finished school last year.

So the pattern is:

• [school/object] + [time expression] + bitirdim

This makes Liseyi geçen yıl bitirdim a very useful model sentence.