Questions & Answers about Tämä on hyvä ajatus.
How is the noun ajatus formed from a verb?
It is derived from the verb ajatella (to think). The suffix -us is attached to the verb's root (ajat-) to create a noun that represents the result of the action: a thought.
How does the word ajatus change when adding case endings?
Nouns ending in -us that are derived from verbs typically change their stem to -ukse- before you add an ending. For example, to say "in a thought", it becomes ajatuksessa. The partitive form is ajatusta.
Is there a difference between ajatus and the loanword idea?
They are often interchangeable in phrases like this, but there is a slight nuance. Ajatus literally means a "thought" coming from your own mind, while idea is generally used for a specific plan, concept, or sudden inspiration.
Why is the adjective hyvä in the nominative case instead of the partitive?
In Finnish "A is B" sentences, the adjective stays in the nominative case if the noun it describes is singular and countable. Because a thought (ajatus) is a countable thing, we say hyvä ajatus. If it were an uncountable substance like water, the adjective would take the partitive (hyvää).