Технический надзор проверил гидроизоляцию.

Because it is the subject of the sentence — the thing that performed the action.

• технический = adjective, masculine singular nominative
• надзор = noun, masculine singular nominative

They match each other in gender, number, and case.

So Технический надзор проверил... means technical supervision / the technical inspector / the inspection authority checked...

It can refer to technical supervision as a function, department, authority, or the responsible inspector/inspection body, depending on context.

In real-life usage, Russian often uses expressions like this more broadly than English does. So even though надзор literally means supervision/oversight, the phrase can stand for:

• the supervising authority
• the inspector
• the technical supervision department
• the person responsible for inspection

So grammatically it is a singular masculine noun phrase, even if in English you might translate it more naturally as the technical inspector or technical supervision.

Проверил is the perfective past tense. It presents the action as completed: the check was carried out and finished.

• проверил = checked / inspected (completed action)
• проверял = was checking / checked regularly / checked for some time (process, repeated action, or no focus on completion)

In this sentence, the idea is that the inspection was completed, so проверил is the natural choice.

That is the normal marker of the past tense in Russian.

Past tense forms are built from the infinitive stem plus forms that show gender and number:

• проверил = masculine singular
• проверила = feminine singular
• проверило = neuter singular
• проверили = plural

Since надзор is a masculine singular noun, the verb is проверил.

Because it is the direct object of the verb проверил, so it is in the accusative case.

The dictionary form is:

• гидроизоляция = waterproofing / hydro-insulation

In the accusative singular, it becomes:

• гидроизоляцию

This happens because it is a feminine noun ending in -я.

Pattern:

• nominative: гидроизоляция
• accusative: гидроизоляцию

So the sentence literally has:

• who? — технический надзор
• did what? — проверил
• what? — гидроизоляцию

Yes, especially in construction and engineering contexts.

It is made up of:

• гидро- = hydro-, water-
• изоляция = insulation / isolation

So гидроизоляция means waterproofing or water insulation.

This is a technical noun, and in construction Russian often uses long compound-like terms of this kind.

Because Russian grammar follows the grammatical form of the subject, not necessarily the real-world number of people involved.

The head noun here is:

• надзор — singular, masculine

So the verb must be:

• проверил — singular, masculine

Even if the phrase refers to a department, authority, or function involving several people, grammatically it is still singular.

Yes. Russian word order is flexible because cases show the grammatical roles.

The neutral order here is:

• Технический надзор проверил гидроизоляцию.

But you could also say:

• Гидроизоляцию проверил технический надзор.
  This puts more focus on гидроизоляцию.

• Проверил гидроизоляцию технический надзор.
  This is possible too, though more marked and context-dependent.

So word order in Russian often changes for focus, emphasis, or style, not for basic grammar.

Because Russian has no articles like a or the.

Whether something is understood as definite or indefinite comes from:

• context
• word order
• shared knowledge
• the situation

So Технический надзор проверил гидроизоляцию could be understood as:

• The technical inspector checked the waterproofing
• Technical supervision checked the waterproofing
• A technical inspector checked the waterproofing

The exact English article depends on context, not on a Russian word.

The stresses are:

• техни́ческий
• надзо́р
• провери́л
• гидроизоля́цию

So one natural pronunciation is:

техни́ческий надзо́р провери́л гидроизоля́цию

This is useful because stress in Russian is unpredictable and can affect pronunciation quite a lot.

Надзор is grammatically inanimate.

Here, that mainly matters less than case and verb agreement, but it is useful to know because in Russian:

• animate masculine nouns often have accusative forms like the genitive
• inanimate masculine nouns often have accusative forms like the nominative

In this sentence, надзор is the subject, so it is nominative anyway. The more important point is that it is masculine singular, which is why the verb is проверил.

Yes. Проверить has a range of meanings including:

• check
• inspect
• verify
• examine

In a construction or engineering context, inspect may sound more natural in English than check.

So depending on context, good translations include:

• The technical inspector checked the waterproofing.
• Technical supervision inspected the waterproofing.
• The inspection authority verified the waterproofing.

The Russian verb itself is broad enough to allow these options.