In French, a few common adjectives are placed before the noun rather than after it. To avoid a clunky pause when the following noun begins with a vowel or a mute h, five of these masculine singular adjectives change their spelling and pronunciation to link smoothly with the next word.
The big three: bel, nouvel, vieil
The adjectives beau (beautiful), nouveau (new), and vieux (old) transform into bel, nouvel, and vieil when placed directly in front of a masculine singular noun starting with a vowel.
| They have just bought a beautiful prestigious building. | Ils viennent d'acheter un bel édifice prestigieux. |
| This old building is a luxurious hotel. | Ce vieil édifice est un hôtel luxueux. |
| We are visiting a new luxurious establishment. | Nous visitons un nouvel établissement luxueux. |
This rule also applies to nouns starting with a mute h, which act just like vowels for pronunciation:
| The welcome in this new hotel is incomparable. | L'accueil dans ce nouvel hôtel est incomparable. |
Normal forms before consonants
These special forms are strictly for pronunciation. If the masculine noun begins with a consonant, you simply use the standard forms (beau, nouveau, and vieux).
| They have just opened a new spa in this beautiful space. | Ils viennent d'ouvrir un nouveau spa dans ce bel espace. |
| The old spa of this old hotel is incomparable. | Le vieux spa de ce vieil hôtel est incomparable. |
Fol and mol
Two other adjectives follow this exact same pattern: fou (crazy/foolish) becomes fol, and mou (soft) becomes mol before a vowel or mute h.
| He has a foolish hope of reserving this prestigious place. | Il a un fol espoir de réserver cet endroit prestigieux. |
Just like the others, you revert to the standard form if the adjective modifies a noun starting with a consonant, or if it stands alone after a verb:
| The bed is soft, but I would like a soft pillow. | Le lit est mou, mais je voudrais un mol oreiller. |