的 (teki) is a suffix that converts nouns into na-adjectives. It gives the meaning of 'having the nature of' or 'characteristic of'. For example, 科学的 (kagakuteki) means 'scientific' in the sense of 'relating to science'. It is very productive, especially with abstract or loanword nouns, and often used in formal or academic contexts.

As a na-adjective, it can modify nouns with な (e.g. 理想的な (risouteki na) 'ideal') and be used predicatively with だ (e.g. 彼は理想的だ (kare wa risouteki da) 'He is ideal'). It can also be used as an adverb with に (e.g. 具体的に (gutaiteki ni) 'concretely').

Be careful: Not every noun can take 的. It is not used for everyday concrete nouns like 'table' or 'cat'. Also, some nouns already have a different adjective form, so check if the 的 form is actually used.