generated at
subtyping
サブタイピング
Covariance and contravariance
The circle-ellipse problem (for the perils of subtyping variable-types on the same basis as value-types)
class-based programming
Top type
Refinement type
Behavioral subtyping

googlesubtyping
Google画像検索subtyping
Google定義検索 subtyping
wikipediasubtyping
weblio subtyping
kotobank subtyping
jisho subtyping