"Since" and "Sense" sound similar so the words are often confused, especially by teenagers. However, both words have completely different meanings.
The word "since" is synonymous with "because" and "from then till now" is among the most common words of the English language. On the other hand word "sense" indicates the five senses of sight, hearing, smell, taste and touch. These are the faculties through which animals and humans perceive stimuli from outside or inside the body.
edit Differences in Meaning and Grammar
"Since" can be used as an adverb, preposition and conjunction in sentences. The way it is used changes its meaning.
"since" as an Adverb
- from then till now: e.g. The dictator has ruled the country since 1985.
- Between a particular past time and the present; subsequently: e.g. She was reluctant initially but has since consented.
- ago; before now: long since. e.g. I haven’t seen her ever since she returned from Far East.
"since" as a Preposition
- Continuously from or counting from: e.g. It has been raining since morning.
- Between a past time or event and the present: e.g. A lot has changed since her wedding.
"since" as a Conjunction
- Because; inasmuch as: e.g. Since you're already here, you might as well help me with the cake.
"Since" is a subordinating conjunction which joins a clause to another on which it depends for its full meaning. E.g. We shall go since that is what you want. (Note that the action of going is dependent on the desire.)
"Sense" is a noun. The word and its derivative sensed are also used as verbs.
"sense" as a Noun
- Any of the faculties, as sight, hearing, smell, taste, or touch: e.g. The five sense organs are our windows to the outside world.
- A feeling or perception produced through the organs of touch, taste, etc: e.g. Touch snow to get a sense of winter.
- A faculty or function of the mind analogous to sensation: e.g. Moral sense is given priority in education of young minds.
- Any special capacity for perception, estimation, appreciation, etc: e.g. His amazing sense of humor has entertained many an evening.
- Usually, senses, clear and sound mental faculties; sanity: e.g. Is she out of her senses?
"sense" as a Verb
- To perceive (something) by the senses; become aware of: e.g. He could sense their presence behind the door.
- To grasp the meaning of; understand : e.g. The child took it in good sense.
Since - From Middle English syns, sinnes, contraction of earlier sithens, sithence, from sithen ("after", "since") ( + -s, adverbial genitive suffix) from Old English siþþan, from the phrase sīþ þǣm "after/since that [time]" from siþ ("since", "after") + þ?m dative singular of þæt.
Sense - Middle English sense from Old French sens, sen, san ("sense, reason, direction"), partly from Latin sensus ("sense, sensation, feeling, meaning"), from sentio ("feel, perceive") (see scent); partly of Germanic origin (whence also Occitan sen, Italian senno), from Frankish *sinn "sense, mental faculty, way, direction" (cf French assener ("to thrust out"), forcené "maniac") from Proto-Germanic *sinnaz ("mind, meaning").