https://en.wikipedia.org/wiki/Proto-Indo-Europeans
Here's a visualization of IE languages, perhaps not accurate in every single detail, but easy to remember:
0 shunya 1 ek 2 do 3 theen 4 char 5 paanch 6 che 7 saath 8 aatuh 9 nau 10 dus
Yeah, PIE (Proto-Indo-European) is very interesting—we think that we're so different but our languages are so similar.
Slovak has two cognates: šifra (cipher: secret writing, plus some related meanings, such as an individual character of a secret writing, an abbreviated signature, or anidentifying mark) and the word cifra (digit). (Probably used a bit less than its synonym číslica).
The word ciferník denotes an instrument or clock dial (also číselník).
http://www.dailymail.co.uk/sciencetech/article-3698184/Liste...
Straight from Buddhist meditation, meaning "emptiness" -> and now it's the basis of math and science. And it's not just zero, take a look at the pronunciation of numerals in Sanskrit:
0 śūnya - Arabic "ṣifr" -> Latin "zephir" -> "zero"
1 éka - Greek "ena" -> Latin "unus" -> English "one"
2 dvi - like the prefix "di-" or "bi-" meaning double, German "zwei" -> English "two"
3 trí - like "three"
4 catúr - like "quatre" in French
5 pañca - like Greek "pénte"
6 ṣáṣ - like six, or "șase" in Romanian
7 saptá - like seven, or "șapte" in Romanian
8 aṣṭá - like German "acht", English "eight"
9 náva - like nine, or "nouă" in Romanian, which also means new in both languages (new sounds like nine)
10 dagan - like Latin "decem"
It's amazing how much Sanskrit is in our languages.