Just go with SIL.

As others have pointed out, these terms are vague in English. I have two brothers-in-law. One is my sister's husband, one is my husband's brother. Different relationships, same name.

Usually it's fine to use this general term, as it indicates an approximate level of closeness. If relevant, I can explain the relationship.

Anonymous wrote:A lot of people don't believe this but your in-law's spouse is also your in-law. So, yes, your wife's sister's wife is your SIL.

They are still related to you "in law" because their children would be your blood (or your wife's blood) relative.

Anonymous wrote:No. Your SIL is the sister of your wife. The SIL's spouse (man or woman is irrelevant ) is simply her spouse , is not your in law.

Not true. My SIL's husband is my BIL.

So OP's SIL's spouse would still be a SIL.

This is interesting. I wonder if my DH thinks of my sibling's spouses as his in-laws. I think he does. But I bet in conversation he would say "my wife's sister in law".

If his sister got married, I'd probably consider her DH my BIL. Though I'm not sure. Hmm.

Anonymous wrote:Yes.

Other cultures have more precise terms for all of these relationships, but English doesn't.

Except in these cultures too, they may not have a defined name for spousal or IL relationships between same gender people.

For example, in Hindi, the sister of the wife is called "Saali". The husband of the sister of the wife is called "Saardhu". In this case, wife of a SIL, maybe one can change the word into a feminine and make it "Saardhuni"?

There should be a way to accommodate these relationships as well. Maybe you can coin a term - "SIL-Wifey". Why not?

However, what if the SIL thinks of her lesbian spouse as the "Husband" in the relationship? Then you may need to think of another word.

I feel since these relationships exist, people should name them appropriately to recognize them.

In my family, we would call her your sister-in-lawlaw

Yes.

Other cultures have more precise terms for all of these relationships, but English doesn't.

Ignore the outdated definition assuming a wife has a husband.

http://dictionary.reference.com/browse/sister-in-law?s=t

sister-in-law
[sis-ter-in-law]

noun, plural sisters-in-law.
1. the sister of one's husband or wife.
2. the wife of one's brother.
3. the wife of the brother of one's husband or wife.

A lot of people don't believe this but your in-law's spouse is also your in-law. So, yes, your wife's sister's wife is your SIL.

Anonymous wrote:No. Your SIL is the sister of your wife. The SIL's spouse (man or woman is irrelevant ) is simply her spouse , is not your in law.

would you call your spouse's sister's husband your SIL's husband? because i'd (and do) call him my brother in law.

No. Your SIL is the sister of your wife. The SIL's spouse (man or woman is irrelevant ) is simply her spouse , is not your in law.

I would say "yes of course" - as I call my wife's sister's husband my "brother-in-law" -

but then I google for dictionary definitions and they generally seem to indicate that the term refers only to spouse's sibling, or to sibling's spouse (and not, as in my example and yours, to spouse's sibling's spouse) -

but I think that my broader definition is nicer, and more common in my linguistic experience -

in any event, same-sex or opposite-sex marriage has nothing to do with it.

Anonymous wrote:My wifes sister is my SIL. Is her wife also my SIL or would I call her my SIL's wife?
( Just in case there is confusion we are all gay. Wife and her sister both.)

Yes, or your wife's SIL.

Yes, but for purposes of differentiation you would have to say their names to someone who knows them, or my SIL's wife, if ever it becomes necessary to make that distinction.

My wifes sister is my SIL. Is her wife also my SIL or would I call her my SIL's wife?
( Just in case there is confusion we are all gay. Wife and her sister both.)