Tic-compulsion continuum

Although much emphasis is put on the difference between tics and compulsions the two are actually related; so much so that there seems to exist a tic-compulsion continuum where each are at opposite ends of the same scale.

Theory
The tic/compulsion divide is more of a continuum where at one end you have the absolutely involuntary tics and at the other, the entirely 'deliberate' compulsions, with all points in between.

Tic-x-|---x---Compulsion

Far left: Tics you just can't seem to feel coming and just seem to 'pop out'.

Cross on left: At round about this point in the scale, you can feel the tics coming and they just sort of 'come out', but there's some feeling of 'just gotta do it' even though you're doing it anyway.

Centre: An example you might find here - which is a typical case of 'tic or compulsion' - is evening up. This is where you feel the need to even something up (e.g. make two things parallel with each other or touch yourself against somthing) which is a need/urge which is fairly conscious but is also often done automatically. Of course, evening up can be more to the left of the centre on the scale or more to the right, but often seems to be somewhere near the middle (or slightly to the right).

Cross on right: These are things which you just have to do and you know this, but when you're used to it, it may come automatically, like counting to ten then jumping once after you swtich on a washing machine, but you think about it as you do it.

Far right: These are conscious 'deliberate' actions done to satisy your needs/urges. They are not automatic but you need to do them.

Tic control
Tics are known as 'semi-involuntary' due to the fact that many people can suppress some of their tics for varying amounts of time, however some people have tics which fall to the far left of the spectrum, whereas some have tics nearer the middle, so some people have control over their tics, some don't. Some people find only some of their tics can be controlled.

That's why tics are often described as 'semi-involuntary' - it's like blinking. You only have a certain amount of control over them, but this in itself is a spectrum:

completely uncontrollable -- alomost controllable

Where it says 'almost controllable', some people might have the sensory tics (some describe it as an 'internal itch') but still quite a lot of control over their tics. At the other end, whether accompanied or preceded by sensory tics or not, the tics just happen with no control at all.

The tics on the right are much more compulsion-like, but are still tics in that they don't involve/are not in response to thought, but rather to feelings.

For example: "'My nose, throat and left upper arm tics are more to the left of the spectrum than my grunts which are more compulsion-like but are not compulsions because...well, because they're not. They're tics. Also, compulsion-like tics (or tic-like compulsions?) of my right upper arm in response to my left upper arm tics (which are to the right of the spectrum) are more to the right as they serve to 'even up' the other arm, but still in a tic-like way (in that they're still automatic, but far more controllable than the left upper arm tic.'"