Languages generally have words that are part of the vocabulary but are normally avoided at least in educated speech and writing. Curse words are the most obvious example. The Finnish curse word perkele (literally: devil) is known by many foreigners, but it is less known that it might be used as a relatively mild curse word in some circles, yet taken as very offensive by many. Young people often use vittu (cunt) very frequently—like a comma, as they say. People may say jumalauta as a strong curse word, despite its being originally a prayer, a shortened form of Jumala, auta “God, help [me]”. The point is that you need to listen to how people speak and then tune your mind and your usage accordingly. It is seldom a good idea to be the first one, or even the second one, who uses a potentially problematic word in a company.
The word neekeri (negro) is nowadays mostly avoided, and e.g. musta (black) is used instead. There are some other words for ethnicity that are more difficult to avoid without knowing current Finnish practices. Mustalainen used to be a normal word for gypsy; now romani is recommended. Sámi people were long called lappalainen, but now saamelainen is regarded as the correct word. Even ryssä (Russian person) was once a neutral word, in the 19th century, but then it became rather negative; the correct word is now venäläinen.
There are also innocent-looking words that are widely avoided. The verb panna means many things like “to put” or “to lay down”, and it also means having sexual intercourse. The possibility of this association has made people widely avoid the verb. Instead of old-style Panen kirjan pöydälle (I’ll put the book on the table) they say Laitan kirjan pöydälle or Pistän kirjan pöydälle, using the verb laittaa or the verb pistää, which are partly synonymous with panna.
There are words that are taboo to many people, while other people see nothing wrong with them. The noun tukka means hair on the top of the head, and it is still used that way by most people. Yet, young people may avoid it due to assumed association with pubic hair and use hiukset, the plural of hius, instead.
The words sika (swine) and lehmä (cow) are normal when referring to living animals. However, they are often avoided when referring to meat from those animals. The generic word sianliha (pork, literally “swine’s meat”) is neutral, but pork chop is much more often called porsaankyljys than siankyljys. The word porsas : porsaan denotes a young swine (pig) in principle, but any pork when referring to meat. The general word for beef is naudanliha, containing the word nauta : naudan that denotes a bovine in general (cow or bull). In commerce and in restaurants, the word härkä : härän (e.g., in häränliha) is often used instead of nauta, even though härkä in principle means “ox” in standard Finnish. For further confusion, the word sonni (bull) is sometimes used when referring to beef, whether the meat actually comes from a cow or a bull.