1. (the 3rd letter of the Roman alphabet)
C, c


2. (the speed at which light travels in a vacuum
the constancy and universality of the speed of light is recognized by defining it to be exactly 299, 792, 458 meters per second)
speed of light, light speed, c: : synonim: prędkość światła
synonim: prędkość światła w próżni

3. ( (music) the keynote of the scale of C major)
C: : synonim: do

4. (the syllable naming the first (tonic) note of any major scale in solmization)
do, doh, ut: : synonim: do

5. (the 3rd letter of the Roman alphabet)
C, c: :