“Sing” and “sung” are both forms of the verb “sing.” They are easily confused, but the two are very different. So how do you know if you can use sang or sung in a sentence?
Sang or Sung
The difference between the two is actually quite straightforward. “Sang” is past tense of “sing,” and “sung” is a past participle form of “sing.”
To form a sentence in a simple past tense, use the form “sang,” for instance: She sang this song on the radio yesterday.
The form “sung” is also used to describe actions that happened in the past but it is used slightly differently. Unlike “sang” it must always be preceded by the auxiliary verb have (has/had). For instance, sung in a sentence is: She has sung this song many times in the past year, or I have sung my heart out this past Saturday.
Although both sentences describe past events, the first one is in simple past, and the second one is in present perfect. Present perfect unlike simple past is used to describe actions that happened in recent past, or an action that occurred several times between some point in the past and now, or an action performed during a period of time that is still ongoing.
“Sung,” like other past participles, is also used to form the passive voice of the verb “sing” when it appears after the auxiliary “be.” For instance: This song was sung by a little girl with a big bow.
The important point to remember is that “sung” always comes after an auxiliary verb but “sang” does not.
Regular vs. Irregular Verbs in English
It might help you to know that the verb “sing” belongs to the large group of irregular verbs in English. Regular verbs are those whose past tense and past participle forms are identical, and both are formed by adding the suffix -ed to the verb. For instance, in the sentence, She walked home yesterday, the verb “walked” is a past tense form of the verb walk, like sang is the past tense of sing. And in the sentence She has walked many miles to get here, “walked” is a past participle (like sung) appearing after the auxiliary verb has to form present perfect.
There are many irregular verbs in English that have two different forms for past tense and past participle. Often, as in the case of sang/sung, these have to be memorized. Here are some more examples of irregular verbs:
Break - broke (past tense) - broken (past participle)
ring - rang (past tense) - rung (past participle)
Drink - drank (past tense) - drunk (past participle)