Translation guide
The most common Japanese word for encyclopedia is 百科事典 (ひゃっかじてん). For online encyclopedias like Wikipedia, 百科事典 is still used, but the name of the site is often used directly.
百科事典
encyclopedia
Referring to a reference work containing articles on many subjects, typically arranged alphabetically.
The standard term for any encyclopedia, whether print or digital. It literally means 'hundred-subject dictionary'.
子供用の百科事典を買った。
I bought a children's encyclopedia.
百科事典で調べてみよう。
Let's look it up in the encyclopedia.
A shorter form meaning 'encyclopedia' or 'reference book'. Often used in compound titles, but can be ambiguous as it also means 'dictionary' in some contexts.
この事典は項目が豊富だ。
This encyclopedia has a wealth of entries.
Used in book titles to mean 'complete collection' or 'encyclopedia' of a specific field. Not a general term for encyclopedia.
『料理大全』という本を読んでいる。
I'm reading a book called 'The Complete Encyclopedia of Cooking'.
Referring specifically to a web-based encyclopedia, often collaborative.
For well-known online encyclopedias, Japanese speakers often use the name as-is (e.g., ウィキペディア). You can also say オンライン百科事典.
ウィキペディアで調べた。
I looked it up on Wikipedia.
オンライン百科事典は便利だ。
Online encyclopedias are convenient.
事典 (じてん) means encyclopedia, while 辞典 (じてん) means dictionary (word definitions). They sound the same but are written with different kanji. 百科事典 is unambiguous.