In French, should we write essai, essaie, essais ou essaies?

In French, the word essai can be written with the endings -/e/s/es depending on the meaning with which it is used:

• The verb essayer (to try) conjugated in the present tense is written: j'essaie, tu essaies, il essaie...
• The verb essayer (to try) conjugated in the imperative tense is written: essaie
• The noun essai (a test, a trial) is written without an e: un essai, des essais

For example:

Essaie de ne pas déborder. <=> Try not to overflow.

J'essaie de m'appliquer au maximum. <=> I'm trying to do my best.

Tu essaies de finir avant midi ? <=> Are you trying to finish before noon?

Je rédige un essai portant sur la révolution écologique. <=> I am writing an essay on the ecological revolution.

Les essais ont donné des résultats satisfaisant. <=> The essays have produced satisfactory results.

Note that the verb essayer (to try) can also be conjugated with a y: j'essaye, tu essayes, il essaye ... Both spellings are correct.