Learn French: L'horloger a commencé à assembler les engrenages hier. - The watchmaker started to assemble the gears yesterday.

In French, many verbs require a specific preposition before an infinitive. Commencer is almost always followed by à when talking about starting an action. You might occasionally see commencer de in older or very formal literature, but in everyday modern French, always stick to commencer à.

Why use the passé composé (a commencé) here instead of the imparfait (commençait)?

The word hier (yesterday) pins the start of the action to a specific, completed point in time. Even though assembling gears is an ongoing process that takes time, the specific act of starting it happened once and is now finished, which triggers the passé composé.

Is an horloger only a clockmaker, since it comes from the word horloge?

While une horloge specifically means a large clock, un horloger is a general term for a watchmaker or clockmaker. The everyday word for a wristwatch is une montre, but the professional who repairs them is still called un horloger.

Are there other meanings for the word engrenages?