"one's mental faculties, conscious cognitive powers, sanity," 1560s, from sense (n.). The meaning "faculties of physical sensation" is from 1590s.

"device giving a signal about some physical activity," 1947, from a shortened form of sensory (q.v.) or an agent noun in Latin form from sense (v.).

c. 1300, "agree to, approve;" late 14c. "admit as true," from Old French assentir "agree; get used to" (12c.), from Latin assentare/adsentare, frequentative of assentire "agree with, approve," from ad "to" (see ad-) + sentire "to feel, think" (see sense (n.)). Related: Assented; assenting.

1854, "a general accord or agreement of different parts in effecting a given purpose," originally a term in physiology; 1861, of persons "a general agreement in opinion;" from Latin consensus "agreement, accord," past participle of consentire "feel together," from assimilated form of com "with, together" (see con-) + sentire "to feel" (see sense (n.)). There is an isolated instance of the word from 1633.

c. 1300, "agree, give assent; yield when one has the right, power, or will to oppose," from Old French consentir "agree; comply" (12c.) and directly from Latin consentire "agree, accord," literally "feel together," from assimilated form of com "with, together" (see con-) + sentire "to feel" (see sense (n.)).

"Feeling together," hence, "agreeing, giving permission," a sense evolution that apparently took place in French before the word reached English. Related: Consented; consenting.

c. 1300, "approval, voluntary acceptance of what is done or proposed," also "agreement in sentiment, unity in opinion," from Old French consente, from consentir "agree; comply," from Latin consentire "agree, accord," literally "feel together," from assimilated form of com "with, together" (see con-) + sentire"to feel" (see sense (n.) ).

In Middle English sometimes in a negative sense, "yielding (to sinful desire); connivance." Age of consent, at which one's consent to certain acts is legally valid, is attested from 1650s.

early 14c., dissencioun, "disagreement in opinion," especially strong disagreement which produces heated debate, from Old French dissension (12c.) and directly from Latin dissensionem (nominative dissensio) "disagreement, difference of opinion, discord, strife," noun of action from past participle stem of dissentire "disagree," from dis- "differently" (see dis-) + sentire "to feel, think" (see sense (n.)).

mid-15c., dissenten, "express a different or contrary opinion or feeling, withhold approval or consent," from Old French dissentir (15c.) and directly from Latin dissentire "differ in sentiments, disagree, be at odds, contradict, quarrel," from dis- "differently" (see dis-) + sentire "to feel, think" (see sense (n.)). Ecclesiastical sense of "refuse to be bound by the doctrines or rules of an established church" is from 1550s. Related: Dissented; dissenting.

The noun is 1580s, "difference of opinion with regard to religious doctrine or worship," from the verb. From 1650s as "the act of dissenting, refusal to be bound by what is contrary to one's own judgment" (the opposite of consent). From 1660s as "a declaration of disagreement." By 1772 in the specific sense of "refusal to conform to an established church." 

Has there ever been a society which has died of dissent? Several have died of conformity in our lifetime. [Jacob Bronowski "Science and Human Values," 1956]

"teach, instruct, cause (someone) to understand," c. 1400, ensense, from Old French ensenser "to enlighten, to bring to sense," from en- "in" (from PIE root *en "in") + sens (see sense (n.)). "From 17th c. app. only dialectal (chiefly northern), or in writers under dialectal influence" [OED].

"that which is lacking in sense, language or words without meaning or conveying absurd or ridiculous ideas," 1610s, from non- "not" + sense (n.); perhaps influenced by French nonsens. Since mid-20c., non-sense, with the hyphen, has been used to distinguish the meaning "that which is not sense, that which is different from sense," not implying absurdity.