Bir dilim ekmek yiyorum.

Because bir dilim ekmek is an indefinite measure expression (“a slice of bread”). In Turkish, direct objects that are indefinite or partitive remain unmarked. Only definite/specific objects take the accusative -i.

• Indefinite: Bir dilim ekmek yiyorum (I’m eating a slice of bread).
• Definite: Bir dilim ekmeği yiyorum (I’m eating that particular slice of bread).

Breakdown of yiyorum (I am eating):

1. Root ye- (to eat)
2. Continuous/progressive suffix -yor- → ye + yor → yiyor
3. First-person singular suffix -um → yiyor + um → yiyorum
   So -yor- marks the present continuous tense, and -um shows “I” as the subject.

bir literally means “one,” but when placed before a countable noun it functions like the English indefinite article “a/an.”

• bir dilim = a slice (one slice)
  If you want to emphasize the quantity “one,” you still use bir, but context tells you if it’s “one” or just “a.”

In Turkish, when a noun follows any numeral (including bir), the noun stays in its singular form. You never add the plural suffix -lar/-ler after a number.

• bir dilim, iki dilim, on dilim (not dilimler)

Both orders are grammatically possible, but the common spoken pattern for partitive/measure phrases is bir dilim ekmek (measure word + noun).

• More natural: bir dilim ekmek yiyorum
• Less common: bir ekmek dilimi yiyorum (still understandable, but you’ll hear the first version far more often)

yiyorum = present continuous (“I am eating,” right now).
yerim = simple present/habitual (“I eat,” as a routine or general fact).

• Ongoing action: Şu anda bir dilim ekmek yiyorum.
• Habitual action: Her sabah bir dilim ekmek yerim.