komugiko wo katta.

It is read こむぎこ.

• 小麦 = wheat
• 粉 = powder / flour

So 小麦粉 means wheat flour, and in many everyday contexts it can simply be understood as flour.

を marks the direct object of the verb.

In 小麦粉を買った, the thing being bought is 小麦粉, so を shows that flour is what was bought.

A very literal breakdown is:

• 小麦粉 = flour
• を = object marker
• 買った = bought

So the structure is basically flour + object marker + bought.

Because Japanese normally uses SOV word order: Subject - Object - Verb.

English says:

• I bought flour.

Japanese says:

• (I) flour bought.

So putting 買った at the end is completely normal.

The subject is omitted.

Japanese very often leaves out the subject when it is already understood from context. So 小麦粉を買った。 could mean:

• I bought flour
• He bought flour
• She bought flour
• We bought flour

In many beginner translations, it is shown as I bought flour, but the Japanese itself does not explicitly say I.

買った is the plain casual past form of 買う.

• Dictionary form: 買う = to buy
• Plain past: 買った = bought
• Polite past: 買いました = bought

So:

• 小麦粉を買った。 = casual / plain
• 小麦粉を買いました。 = polite

Both are grammatically correct. The difference is mainly level of politeness.

買う is a う-verb. For this type of verb, the past plain form often changes -う to -った.

So:

• 買う → 買った

This same pattern appears in other verbs too:

• 会う → 会った
• 使う → 使った

So 買った is just the normal past-tense form of 買う.

Although it is written を, the particle is pronounced お in modern Japanese.

So this sentence is pronounced roughly:

こむぎこ を かった
with the particle sounding like o.

You will still see it written as を because that is the standard spelling for the object marker.

No. In normal Japanese writing, this would usually be written without spaces:

小麦粉を買った。

Spaces are often added in textbooks or beginner materials to make the sentence easier to read.

Japanese does not use articles like English does.

So 小麦粉を買った。 could mean:

• I bought flour
• I bought some flour
• I bought the flour

Which one sounds best depends on context. Japanese often leaves that kind of detail unstated unless it is important.

Not in this sentence, if 小麦粉 is the thing being bought.

を is correct because 小麦粉 is the direct object of 買った.

If you said 小麦粉が買った, it would sound like the flour bought..., which does not make sense unless the flour were somehow the subject doing the action.

So for buying flour, を is the right particle.

Yes, it is a natural simple sentence in casual Japanese.

By itself, it sounds like a short statement such as:

• Bought flour.
• I bought flour.

Japanese often allows this kind of short sentence, especially in conversation, notes, diaries, or when the context is clear.

Yes. The polite version is:

小麦粉を買いました。

This is better for speaking politely to someone you do not know well, a teacher, a customer, a coworker in a formal setting, and so on.

The original 小麦粉を買った。 is plain and casual, so it fits friends, family, casual narration, or inner thoughts.