What part-of-speech will the new "because" be? because happy / sad / bored; because science /

Solution 1:

Because' has become a preposition, because grammar.

The word "because," in standard English usage, is a subordinating conjunction, which means that it connects two parts of a sentence in which one (the subordinate) explains the other. In that capacity, "because" has two distinct forms. It can be followed either by a finite clause (I'm reading this because [I saw it on the web]) or by a prepositional phrase (I'm reading this because [of the web]). These two forms are, traditionally, the only ones to which "because" lends itself.

Read more:

http://www.theatlantic.com/technology/archive/2013/11/english-has-a-new-preposition-because-internet/281601/