Does the twitter streaming api return plural words? For example, if I query for 'bike', would the returned tweets include 'bikes'? or include 'dutchbike'? or 'bikelane'?
You can find a definitive answer in the Twitter docs. Read the description of the track parameter here: https://developer.twitter.com/en/docs/tweets/filter-realtime/guides/basic-stream-parameters.
The answer is that when you filter for a word such as "bike" you will get tweets with any form of "bike" (case insensitive). So, all your examples would be included.