Why do a number of languages have similar words?
This is a very interesting question and opens other questions as well. There are many words in different languages that sound similar or even the same. The wonderful answers of the other tutors give examples of languages using only the Latin alphabet.
One look at the Slavic languages. For example the word "heart" in all Slavic languages sounds almost the same. Several examples:
Bulgarian - surce, Macedonian - srce, Russian - serdce, Czech - srdce, Croatian - srce, Serbian - srce, Slovac - srdce, Slovenian - srce, Polish - serce.
Notice that they use two different alphabets - Cyrillic and Latin, but the word sounds so similar in the different languages! (The site does not use Cyrillic, so I cannot write the words with the right letters here, sorry.) Back in the time when tribes were travelling from a place to another place, they were very often sharing land, and respectively - words, customs, culture... Geographically close, they developed many similar things together.
Languages that have a common Latin root, share words, too, as the tutors before me wrote.
But how about some words that sound very similar in languages that don't have anything in common, like the word "no" , for example? One can find more than 30 languages (from different Language families) in which the word "no" sounds so similar, or at least starts with the sound "n"! Including Japanese. (But excluding Greek in which the word "no" is pretty exotic "ohi" (oxi).)
Languages borrow words from one-another. Words like "computer" and "Internet" cross language barriers and don't need translation in any language. As the world is getting smaller, and people are travelling everywhere, more words get accepted in different languages.
Languages are fascinating! There is a saying: "One lives as many lives as many languages one speaks."