A kind of
Definition 1 of 2
Pro Tip 1/3General Category
Use 'a kind of' to classify something broadly when specific details aren't necessary. 
The platypus is a kind of mammal that lays eggs.
Pro Tip 2/3Avoid Overuse
Be cautious of overusing 'a kind of' when you can name the exact category. 
A rose is a kind of flower, but more precisely, it's a shrub.
Pro Tip 3/3Not Always Literal
Sometimes 'a kind of' is used figuratively to express similarity, not literal classification. 
His music is a kind of therapy for many.