Ok, word/grammar/English "geeks" out there............??

"sang" is the past tense of "to sing"

"sung" is the past participle. that means you only use 'sung' when it's preceded by 'has' or 'have' or 'had'.

e.g.

She sang wonderfully tonight.

She has sung better in the past.

To pull together what's been said (at least, that which is correct!)and flesh it out a bit:

"sang" is used ONLY for the simple past tense: "I sang the song."

"sung" - This form is called a "past participle". It is used chiefly in perfect & passive forms

(You will hear some folks use it for the simple past tense --"I sung the song." --but this is NOT standard English)

PERFECT =with forms of the auxiliary verb "have"

(Incidentally, the perfect forms all by themselves do NOT indicate how many times something is done -- "I have sung it." may be used whether you did it once or repeatedly.)

Three active & three passive tenses--

* Present perfect: I have sung the song.

passive - The song has been sung.

* Past perfect (pluperfect): I had sung

passive - The song had been sung.

* Future perfect: I will (or shall) have sung

passive -The song will have been sung.

PASSIVE =with forms of the auxiliary verb "be"

In addition to the perfect forms listed above

*present: It is sung.

*past: It was sung.

The perfect aspect can also be combined with various modal auxiliary verbs, such as would, should, could, may or might

* Conditional perfect ('would'): I would have sung (if I had been there).

passive - The song would have been sung.

* should/could/may/might

perfect: I should have sung an easier song.

passive -The song should have been sung.

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Just to fill out the grammar. The past participle of verbs is also used in many cases as an ADJECTIVE (For example -the past participle "baked" is used as as verb in "We had baked a nice cake." We use it as an adjective in, "The baked beans tasted delicious.")

Technically, there is no reason "sung" couldn't be used this way, but it's doubtful you'll find anyone doing so (though we DO use "UNsung" as an adjective).

Sang is simple past while sung is past participle.

We use the simple past to talk about a single finished action that started and finished in a determinate time in the past.

We use the past participle to show that such action has been performed several times in the past and might continue in the future but we dont specify the time it happened.

Example:

I sang that song once at a Karaoke bar.

Ive sung that sung at every karaoke bar I've been to.

The "Rule of Thumb" that I learned way back when is to always use 'sang' as an action being performed by a person. 'Sung' is used when the topic is the song/piece itself.

"She SANG a beautiful aria."

"Precious Memories was SUNG at her funeral."

He really sang that song there, it was really sung like a pro. Ok... That is bad but it works.

I sang.

She sang.

He sang.

We sang.

The song "Kiss",by Prince, was sung.

I sang a song yesterday.

I haven't sung in a while.

She/he/they sang a song. He/she/they, have sung.

sang is past tense, as in...He sang the song well last night.

Sung is RARE past tense, according to my trusty Websters New world dictionary 1968 edition.

"Its hard hard to learn to sing in a studio apartment but I wish he had sung it when I wasn't here." She said as she handed the police the empty pistol...