Le contrôleur technique décèle l’usure.

In French, most adjectives come after the noun, not before it.

So:

• un contrôleur technique = a technical inspector / vehicle inspector

Here, technique is an adjective describing contrôleur.

English often puts adjectives before the noun, but French usually puts them after:

• une voiture rouge = a red car
• un contrôle technique = a technical inspection

So contrôleur technique follows the normal French pattern.

No. In this sentence, technique is an adjective, meaning technical.

So le contrôleur technique means something like:

• the technical inspector
• or, depending on context, the vehicle inspection officer

French often uses words that look like English nouns as adjectives too. Here, technique is not a separate noun meaning a technique.

Because usure starts with a vowel sound, la becomes l’ before it.

This is called elision.

• la voiture → no change
• la machine → no change
• la usure → l’usure

French avoids the clash of two vowel sounds, so the article shortens.

Usure is feminine, which is why the full article would be la.

You usually have to learn noun gender along with the noun:

• l’usure = feminine
• dictionary form: usure (f.)

Even though the article is shortened to l’, the noun still keeps its gender. So l’usure is still feminine, not neutral.

French normally uses articles much more often than English does.

So in a sentence like this, French usually wants:

• Le contrôleur technique
• l’usure

Leaving out the articles would sound unnatural or ungrammatical in standard French.

French often prefers:

• Le chat mange la souris rather than
• Chat mange souris

So the presence of le and l’ is completely normal.

Décèle is the present tense, third person singular, of the verb déceler.

So it means:

• he detects
• she detects
• it detects
• or here, the inspector detects

Because the subject is Le contrôleur technique, the verb takes the il/elle/on form:

• je décèle
• tu décèles
• il/elle décèle
• nous décelons
• vous décelez
• ils/elles décèlent

This is a spelling change that helps show pronunciation.

The infinitive is:

• déceler

But in some forms, the e in the stem changes to è:

• je décèle
• tu décèles
• il/elle décèle
• ils/elles décèlent

This happens in many French verbs where pronunciation would otherwise be less natural.

A similar pattern appears in verbs like:

• acheter → j’achète
• lever → je lève

So déceler → décèle is a normal stem change.

It is pronounced approximately like:

• day-sell

More precisely in French IPA:

• /de.sɛl/

A few pronunciation points:

• dé- sounds like day
• -cèle has an open è sound, like sel in French
• the final e is not pronounced separately

So décèle is one smooth two-syllable word.

There is no special liaison in either place.

• technique décèle: no liaison
• l’usure: this is not liaison; it is elision

That second one is important:

• elision = dropping the vowel of la/le before a vowel sound
• liaison = pronouncing a normally silent final consonant before a following vowel

Example of liaison:

• les amis → the s is pronounced like z

But in l’usure, the article is simply shortened.

Because French word order here is the normal Subject + Verb + Object pattern, just like English.

• Le contrôleur technique = subject
• décèle = verb
• l’usure = object

So the structure is:

• The technical inspector detects wear

This is one of the easiest parts of the sentence for English speakers, because the order is very familiar.

Yes. The exact English choice depends on context.

Déceler often means:

• to detect
• to spot
• to identify
• to uncover

In this sentence, detects is probably the most neutral translation. But in real life, if the context is inspection or diagnosis, English might also use:

• spots signs of wear
• identifies wear
• detects wear

So déceler is a fairly formal or precise verb meaning to notice something that may not be obvious at first.

Usually, yes, contrôleur refers to a person whose job is to inspect, check, or supervise something.

Depending on context, it can mean:

• inspector
• controller
• examiner
• ticket inspector
• quality-control officer

In contrôleur technique, it strongly suggests a professional inspector, not a machine.

If you were talking about a machine or device, French would more often use other words depending on the context.

It can do either, depending on context.

The French present tense can mean:

• a specific present action: The inspector is detecting wear
• a general truth or habitual action: The inspector detects wear

Without more context, this sentence is usually read as a simple present statement:

• The technical inspector detects wear

French present tense is often broader than the English simple present, so context matters.