【Tendency】 , 【trend】 ,  【drift】 ,  【tenor】  can mean a movement or course having a particular direction and character or the direction and character which such a movement or course takes.

【Tendency】  usually implies an inherent or acquired inclination in a person or thing that causes him or it to move in a definite direction so long as no one or nothing interferes. Often, when used in reference to persons, the word means little more than leaning , propensity , or disposition .

More often, especially when used in reference to groups or communities or their activities or the course or direction they take with or without consciousness or intent, the term implies a driving force behind the direction or course taken and an insusceptibility to its being controlled or changed.

【Trend】 is used primarily in reference to something that follows an irregular or winding course and denotes the general direction maintained in spite of these irregularities.

In its extended use  【trend】  may differ from  【tendency】 in implying a direction subject to change through the interposition of a sufficiently strong force or agency, in implying a course taken at a given time by something subject to change and fluctuation, or in implying the general direction followed by a changing or fluctuating thing throughout its entire course or within given limits of space or of time.

【Drift】 may apply to a 【tendency】 whose direction or course is determined by such external influences as a wind or the movement of flowing water or a fashion or a state of feeling, but it may apply also to the direction or course taken by something (as speech, writing, or teaching) that has a meaning, a purpose, or an objective which is not definitely stated or made clear but which is inferable; in this sense the word is scarcely distinguishable from intention , purport , or import .

【Tenor】  is a very close synonym of  【drift】 in this latter sense but it more often refers to utterances or documents and carries a much stronger implication of clearness of meaning or purport.

Both in this sense and in its more common sense of a course or movement having a particular clearly observable direction  【tenor】 carries a strong implication of continuity in that course and of absence of fluctuation in its direction; therefore it frequently suggests unaltered, often unalterable, procedure.