du, de

In French, "du" and "de" are both contractions of the preposition "de" with the articles "le" or "la". Here's when to use each:

1. "Du" is the contraction of "de" + "le" and is used before masculine nouns:

   - Ex: Je mange du pain. (I am eating some bread.)

2. "De la" can be contracted to "de l'" before a feminine noun starting with a vowel or mute "h". 

   - Ex: Je bois de l'eau. (I am drinking water.)

3. "De la" is also used before feminine singular nouns:

   - Ex: J'ai de la chance. (I am lucky.)

4. "De l'" is used before masculine or feminine singular nouns starting with a vowel or mute "h":

   - Ex: J'ai de l'argent. (I have some money.)

5. "De" is used before plural nouns, regardless of gender:

   - Ex: Je veux des pommes. (I want some apples.)

So, "du" is specifically for masculine singular nouns, while "d'" is used before singular nouns starting with a vowel or mute "h", regardless of gender.