За час до вебинара я проверю микрофон и камеру.

An hour before the webinar, I will check the microphone and the camera.

Breakdown of За час до вебинара я проверю микрофон и камеру.

• я: I
• и: and
• проверить: to check
• до: before

Questions & Answers about За час до вебинара я проверю микрофон и камеру.

What does за час до вебинара mean, and why are there two prepositions?

This is a very common Russian time pattern:

за + amount of time + до + event

So:

• за час = by an hour / one hour before
• до вебинара = before the webinar

Together, за час до вебинара means an hour before the webinar.

Russian often uses both parts in this expression. It is the normal way to say that something happens a certain amount of time before another event.

Examples:

• за день до поездки = a day before the trip
• за пять минут до урока = five minutes before class

Why is it вебинара and not вебинар?

Because до requires the genitive case.

The base form is вебинар. After до, it changes to вебинара.

So:

• вебинар = webinar
• до вебинара = before the webinar

This is a rule you will see very often:

• до урока = before the lesson
• до встречи = before the meeting
• до работы = before work

Why is it час and not часа?