Compramos el disco ayer.

Because compramos can mean either we buy (present) or we bought (preterite), depending on context.

In this sentence, ayer = yesterday, so the time expression makes it clear that the sentence is in the past:

• Compramos el disco ayer. = We bought the record yesterday.

Without context, compramos is ambiguous. With ayer, it is clearly past.

Spanish often leaves out subject pronouns when the verb already shows who is doing the action.

• Compramos already tells you the subject is we.

So:

• Compramos el disco ayer.
• Nosotros compramos el disco ayer.

Both are correct, but the version without nosotros is more natural unless you want emphasis or contrast:

• Nosotros compramos el disco, no ellos.
  = We bought the record, not them.

In Spanish, articles like el, la, un, and una are used more regularly than in English.

Here, el disco means the record / the album / the disc.

If you said just Compramos disco ayer, it would sound incomplete or unnatural in standard Spanish. You normally need an article or some other determiner:

• Compramos el disco = We bought the record
• Compramos un disco = We bought a record
• Compramos ese disco = We bought that record

Disco can mean a few things depending on context, but in a sentence like this it most commonly means:

• record
• album
• disc

In modern everyday use, it often refers to a music album. The exact English translation depends on context.

So el disco could be:

• the record
• the album

That word order is very natural in Spanish. Time expressions like ayer can often go in different positions.

All of these are possible:

• Compramos el disco ayer.
• Ayer compramos el disco.

The meaning is basically the same. The difference is usually one of emphasis or style:

• Ayer compramos el disco. puts more focus on yesterday
• Compramos el disco ayer. sounds very neutral and natural

Yes, absolutely.

Spanish word order is more flexible than English word order. Moving ayer to the front is common and correct:

• Ayer compramos el disco.

This often emphasizes when it happened.

In Spanish from Spain, both the preterite (compramos) and the present perfect (hemos comprado) are used, but they are not used in exactly the same situations.

With a finished past time expression like ayer, the normal choice is the preterite:

• Compramos el disco ayer.

Using hemos comprado with ayer is generally not standard in Spain.

Very roughly:

• compramos = we bought
• hemos comprado = we have bought

In Spain, the present perfect is more often used for actions connected to the present time frame, for example:

• Hoy hemos comprado un disco. = Today we have bought a record / We bought a record today.

But with ayer, use the preterite.

No. It is spelled the same and pronounced the same.

So the only way to know whether it means we buy or we bought is from context:

• Normalmente compramos discos aquí. = We usually buy records here.
• Compramos el disco ayer. = We bought the record yesterday.

The time word ayer removes the ambiguity.

Because it follows the normal Spanish stress rules, so no written accent is needed.

Compramos is stressed on the second-to-last syllable:

• com-PRA-mos

Words ending in -n, -s, or a vowel are normally stressed on the second-to-last syllable, so no accent mark is necessary unless the stress is irregular.

No. In correct English, that would be ungrammatical, and in Spanish the word ayer clearly places the action in the past.

So in this sentence, the only sensible reading is:

• We bought the record yesterday

The form compramos is only ambiguous when there is no context.

Because verb + object is the normal, neutral order in Spanish, just as in English:

• Compramos = We bought
• el disco = the record
• ayer = yesterday

So the structure is:

verb + object + time expression

That is the most straightforward and natural way to say it. Spanish can change word order for emphasis, but this version is the basic one.

Not normally, if you mean a completed action like we bought the record yesterday.

Comprábamos is the imperfect, which is usually used for:

• ongoing past actions
• repeated past actions
• background description

So Comprábamos el disco ayer would sound odd in most contexts.

For a finished action completed yesterday, Spanish uses the preterite:

• Compramos el disco ayer.

That tells us the purchase happened and was completed.