"TENT," "TENSIVE," "Tenacious," "Thin," "Tone"

       The American Heritage Dictionary's appendix on Indo-European roots helps me trace out the connections.  Ten- is the Indo-European root of a whole host of words.

       It means "to stretch."  The first group of derivatives bears the exact basic meaning, " "to stretch."  So "tense," for example, means "stretched tight," and that applies to "tension" and "tensiveness."  In the same group is a word I wouldn't have thought of:  "tent," which is material "stretched tight" over poles; to "extend" is to "stretch out from," and so on.  This group arrives through the Latin word for "to stretch," tendere.