What is the abbreviation for they would?

There isn't a standard abbreviation for "they would." You can use:

* They'd (This is the most common and generally accepted abbreviation.)

* 'd (This is acceptable in informal writing, but it's best to use "they'd" for clarity in most situations.)

Remember, abbreviations are often context-dependent. It's best to choose the option that fits the tone and formality of your writing.