greek help?

hi there kostas, i've been thinkin of tattooing the greek equivalent of 'strength' on my calf for abt a year now, but the online translations offer a few different translations. they are ??????????, ??????, ?????, ????, ????????? most online translators give ??????, but i'd like to know what the rest mean... i dont understand any of these, or rather how the greek language works, so which is more approriate? why are there so many variations of the same word? i chose greek cos i wanted something which isnt too blatantly obvious, like having it tattooed in english. does it sound lame to you?

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