Learn French: J'accepte la clause à condition qu'elle soit claire. - I accept the clause provided that it is clear.

The word soit is the subjunctive form of être (to be). We must use the subjunctive here because the phrase à condition que (provided that) sets a specific requirement that may or may not be fulfilled. This element of uncertainty triggers the subjunctive mood in French.

Could I just use si (if) instead of à condition que?

Yes, you could say si elle est claire (if it is clear). The phrase à condition que is simply a bit stronger and more specific, much like saying 'provided that' or 'on the condition that' in English. Just remember that si is followed by the normal present tense (est), whereas à condition que forces you to use the subjunctive (soit).

Why does the word que become qu' before elle?

The word que always drops its final e and takes an apostrophe when it is followed by a word starting with a vowel, such as elle. This makes the words flow together smoothly as qu'elle.

Why is there an e at the end of claire?