Learn English – always use “‘d” as contraction of “did”

contractionsword-usage

Two different answers for a question say that 'd in "How'd you know?" is a contraction of did.
Can I always use 'd as contraction of did, or should I use it only when 'd follows a word that is part of a set of words?

For example, could I write "I'd know it." or should I write only why'd, who'd, where'd, when'd, and how'd?

I checked the NOAD, but it says that 'd is a contraction for had and would; the same is said from the OALD, which says that he'd is a short form for he had or he would. Both the dictionaries didn't help to understand when I could use 'd instead of did.

Best Answer

You can only contract did (or any other word, for that matter) when it is unstressed.

You cannot, for instance, contract "I did know it", because did is only used there to give emphasis to your assertion that you knew it: "I did know it".

And you can't contract did when it is the main verb of an indicative sentence, or (as David Schwartz points out) the 'stranded' tensed verb of a clause:

✲I'd it. for I did it.
✲He didn't know it, but I'd. for He didn't know it, but I did.

But in questions headed by an interrogative, when did is only there for DO-support, the interrogative takes the emphasis, and did can be contracted.

  • How'd you do it? ... Note that in speech the 'd you will ordinarily be elided to /dʒə/, "Howdja do it?"
  • Why'd he do it?
  • When'd they do it?

✲ marks a usage as unacceptable

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