Singular/plural

I would go with the singular.

It depends on what your meaning is. Singular refers to a particular interaction, in this case. Interactions could be past, ongoing, and future, or just past. I don't know the context of the sentence, which would help. Limit it/them how? In duration? Topic? How?

Oh, sorry. Here's the context: I wasn't able to reply to my friend for a couple of days because I was sick. So, when I recovered, I decided to send him a message that reads: "I'm sorry if I was not able to respond to your messages. I wasn't trying to limit our interaction/s. I just didn't have the energy to respond as I was very sick."

Given that context, I prefer "interactions". You're referring to a specific series of interactions, not the idea of interaction itself.

Agree with hightor; however, it's a weird phrasing that one wouldn't normally use with a friend.

You said: "I'm sorry if I was not able to respond to your messages. I wasn't trying to limit our interaction/s. I just didn't have the energy to respond as I was very sick."

There is no need for the word 'if' in sentence one as it is obvious it wasn't 'iffy' - you did NOT respond, no ifs ands or buts about it.

I would delete the second sentence and just move on to the third. The whole thing could be said much more informally (to a friend) as such:

"So sorry I haven't responded but I've been so sick (under the weather, etc)."

Thanks! But I have another question. Which word should I use with the word "interactions" less or fewer? I feel like "less" would be correct, but I am not entirely sure. The word has a plural form and dictonaries say it can either be a countable noun or an uncountable noun, so I would assume fewer is also possible

You know, you can Google this yourself.

'Fewer' and 'Less'
There's a commonly repeated rule about fewer and less. It goes like this: fewer is used to refer to number among things that are counted, as in "fewer choices" and "fewer problems"; less is used to refer to quantity or amount among things that are measured, as in "less time" and "less effort."

I already did, but I am still confused. Thats why I'm asking

I see a lot of people using the word less with interactions which is why i said "I feel like less would be correct". I rarely see them use fewer with interactions despitr it being countable, so this adds more confusion to me

A lot of people use words incorrectly. People may still be understood but that doesn't mean that they are speaking the language correctly.

Mame's rule is easy to apply.

You can count how many interactions have occurred. You think they have been happening too often. You would prefer fewer interactions.

Now, say you are thinking about how you use your time, and you're starting to resent how much time you spend corresponding with different people. You decide that, in general, you would prefer less interaction.