On an almost-daily basis, I talk to people with five or six different native languages, none of which are English. So, since I don't speak Finnish and German and Spanish and Swedish and Dutch, and my Icelandic is a bit weak, it's usually my native language that we all end up speaking. I've realized that I have altered the way I use my own language- I enunciate more and select different words. Given the mixed influences on my accent already, I hadn't noticed it myself, but it's enough that a sharp-eared friend from my Boston days noted it a few months ago.
One of the things I love about speaking with people who may not have all the words they want to describe things is all the other ways to get the point across, from miming, to using the words in their own language (context and a little linguistic knowledge makes decent guesses often possible) to poetic, and sometimes roundabout ways of describing what they mean. Some of these frills are so lovely that I want to always use them now. For example, wouldn't you rather have a "movement package" when moving flats than just a regular old box? On some occasions, even brand-new words surface.
The ultimate goal of language is to communicate and these people all do so admirably, but the twist of unexpected input has added new flavor to the way I think about the world and the way I use and perceive my own words. Each one of these other languages have their own rules and spelling that spills over into the use of English- v's and w's are exchanged, pre-aspiration floats into words like "not" (this is the little breathy exhale that happens when pronouncing double-consonants in Icelandic and exists in very few languages worldwide), and the Germans and the Icelanders both have the same sprightly way of saying "I think.." Dutch people always sound far too enthusiastic early in the morning with the rising tones at the end of words like "hoiiiii!!" (a Dutchman saying "hi"), and there is definitely something similar about how the pronuciation of Finns and Icelanders appear in English.
This feast of phonemes has been a real treat, showing in real-time just how related the languages are. I studied linguistics in college but it's nothing like actually hearing these words in a way that lays the connections so bare. I'm always scurrying to the dictionary to inspect the roots of an English word, comparing notes with these other languages for where the usages diverged. For example, a few weeks ago I had a very involved discussion about the Icelandic word lóð (pronounced like "loathe"), which means a weight or a building lot. The trail wound through loathe and load and lode and lot and lade, proving unresolved in the end, but left me feeling moreso than ever that we're all not so different after all. Aren't we practically speaking the same language?