Портной записал мерки.

Because it originally is an adjective-type form that is used as a noun. Russian has a number of words like this. Портной means tailor, but it declines like an adjective:

• nominative: портной
• genitive: портного
• dative: портному
• etc.

So even though it means a person and functions as a noun, its endings follow the adjective pattern.

It is in the nominative singular, because it is the subject of the sentence: the tailor is the one doing the action.

So in Портной записал мерки, the structure is:

• Портной = subject
• записал = verb
• мерки = direct object

Записал comes from записать, which usually means to write down, to note down, or to record. It is a perfective verb, so it presents the action as completed.

That matters here because the sentence describes a finished result: the tailor wrote the measurements down.

Compare:

• писал = was writing / wrote, with focus on the process or repeated action
• записал = wrote down, completed the act of recording

So записал is a very natural choice in this context.

It shows that the verb is in the past tense. In Russian past tense, the verb also agrees with gender and number:

• записал = masculine singular
• записала = feminine singular
• записало = neuter singular
• записали = plural

Since портной is masculine singular, the verb is записал.

Мерки is the accusative plural of мерка in this sentence, because it is the direct object of the verb.

For inanimate nouns in Russian, the accusative plural is often the same as the nominative plural. That is what happens here:

• nominative singular: мерка
• nominative plural: мерки
• accusative plural: мерки

So the sentence uses мерки because the tailor wrote down multiple measurements.

In this context, мерки means measurements, especially body measurements used for making clothes.

This is a very common tailoring context. For example:

• снять мерки = to take measurements
• записать мерки = to write down the measurements

So this is not just any kind of measuring in general; it strongly suggests clothing or fitting.

Because tailoring normally involves several measurements, not just one. For example, chest, waist, sleeve length, inseam, and so on.

Russian can use the singular мерка when referring to a single measurement, but in real-life tailoring situations, мерки is much more natural because multiple measurements are usually taken and recorded.

The word order Портной записал мерки is the most neutral and straightforward order: subject + verb + object.

Russian word order is more flexible than English, because case endings help show grammatical roles. So other orders are possible, for example:

• Мерки записал портной
• Записал портной мерки

But those alternative orders would usually change the emphasis or sound more marked. The original order is the basic, neutral way to say it.

Russian has no articles, so it does not use separate words like the or a/an.

That means Портной записал мерки could be understood in English as:

• The tailor wrote down the measurements
• A tailor wrote down the measurements
• sometimes even The tailor wrote down some measurements

Which English version is best depends on context, not on a special article in Russian.

The normal stress is:

• портно́й
• записа́л
• ме́рки

So the whole sentence is pronounced:

портно́й записа́л ме́рки

Stress is important in Russian, because it is not always predictable and can affect pronunciation quite a lot.

Yes, depending on context, записал can sometimes mean recorded, entered, or noted down, not necessarily writing with pen and paper.

But with мерки, the most natural interpretation is still wrote down the measurements or recorded the measurements. In other words, the tailor took the information and put it into some form of record.