What has 4 in the morning 3 at lunch and 2 in the evening?

The answer to the riddle is the letter "o." In the Word "morning," there are four letters 'o' (if counted as part of the phrase "4 in the morning"), in "lunch," there are three letters 'o' (if interpreted as part of the phrase "3 at lunch"), and in "evening," there are two letters 'o' (if interpreted as part of the phrase "2 in the evening"). Thus, it plays on the frequency of the letter 'o' during those times of day.