L’expert commence l’expertise.

Because both nouns are being used with the definite article le or la, and before a vowel sound French normally shortens the article to l’.

• le expert becomes l’expert
• la expertise becomes l’expertise

This is called elision. It happens to avoid a clash of vowel sounds.

Even though the written form is the same, the gender is different here:

• l’expert = masculine singular
• l’expertise = feminine singular

The apostrophe shows that a vowel has been dropped.

• le
  • expert → l’expert
• la
  • expertise → l’expertise

So the apostrophe is not showing possession, as it often does in English. In French, here it simply marks the missing vowel from the article.

Because commence is the third-person singular present tense of the verb commencer, which means to begin or to start.

So:

• je commence = I begin
• tu commences = you begin
• il / elle / on commence = he / she / one begins

In L’expert commence l’expertise, the subject is l’expert, which is singular, so the verb must be commence.

Because in this sentence commencer is followed by a direct object noun, not by another verb.

• L’expert commence l’expertise. = The expert begins the assessment.

But when commencer is followed by a verb, French often uses à:

• L’expert commence à parler. = The expert begins to speak.

So:

• commencer + noun → no à
• commencer à + infinitive → with à

Not always. This is an important false-friend issue.

In English, expertise usually means special skill or knowledge.

In French, expertise can mean that too in some contexts, but very often it means an expert assessment, appraisal, evaluation, or examination, especially in technical, legal, insurance, or medical contexts.

So in this sentence, l’expertise is probably not expert skill in the abstract. It more likely means the expert examination/appraisal.

Because French word order here is the normal subject + verb + object order, just like in English.

• L’expert = the subject, the person doing the action
• commence = the verb
• l’expertise = the object, the thing being started

So the structure is very straightforward:

The expert + begins + the assessment

Yes, it matters.

• expert is usually masculine here: l’expert
• expertise is feminine: l’expertise

Gender matters because it affects the article:

• masculine: le → l’ before a vowel
• feminine: la → l’ before a vowel

You cannot see the gender directly from l’, so you have to know the noun itself.

Also, if the noun expert referred to a woman, you would usually say l’experte.

A careful approximate pronunciation is:

Lex-per com-mons lex-per-teez

A more accurate IPA version is:

lɛkspɛʁ kɔmɑ̃s lɛkspɛʁtiz

A few useful notes:

• l’expert begins with a clear eks sound.
• The r in French is the French r, not the English one.
• commence has a nasal vowel in the second syllable.
• expertise in French is pronounced more like eks-pehr-teez, not exactly like the common English pronunciation.

Not really in the usual sense learners first study.

There is elision in l’expert and l’expertise, but not an extra pronounced liaison consonant between separate words like in les amis.

However, when speaking, l’expert and l’expertise flow smoothly because the article has already reduced to l’ before the vowel.

So the key phenomenon here is elision, not a classic liaison example.

Grammatically, you might hear other verbs depending on context, but commencer is the most natural basic verb for to begin/start here.

• commencer = the standard neutral choice
• débuter can sometimes be used, but it is often less natural with a direct object in many everyday contexts

So for a learner, L’expert commence l’expertise is a good, clear model sentence.

Yes, it can feel repetitive, because expert and expertise are closely related words.

French does allow this kind of repetition, especially in technical or formal contexts. It may sound slightly stylistic, formal, or even deliberately illustrative in a teaching sentence.

So the sentence is grammatically fine, but in real life a native speaker might sometimes choose a more varied phrasing depending on the context.