The instrument of thought is language, otherwise known as INNER SPEECH. This variety of language may not necessarily be as well-formed as speech when exteriorized, but no matter how fragmentary, it is recognizably language. Moreover, we may actually choose from possible lexical variants (like synonyms) in clothing inner speech in the dress that answers to our thought.
Thus, to give a fresh example from the real life of your humble blogger, today I was about to cross the street at the corner of York Avenue and East 80th Street in Manhattan, when I looked around me and noticed the considerable variety of human types in my immediate vicinity. I then verbalized it to myself by forming the sentence, “There’s quite a mixture here,” but then quickly changed the form to, “There’s quite a mélange here.” Why I chose to replace the ordinary word mixture with the French mélange is not altogether clear, except that when I made the change, I thought to myself, “Mélange is more apt.” It is, after all, a borrowing from French, and thereby conjures up all kinds of semantic associations that are not coincident with those of the English word mixture. There is in fact no such thing as perfect synonymy, synonyms always differing from each other in one or more respects.
Such is the variability of inner speech, the language of thought––even about the most quotidian things in one’s life.