Butterfly and Throttle valve

Butterfly noun - Diurnal insect typically having a slender body with knobbed antennae and broad colorful wings.

Throttle valve and butterfly are semantically related. In some cases you can use "Throttle valve" instead a noun "Butterfly".

Throttle valve noun - A valve that regulates the supply of fuel to the engine.

Butterfly and throttle valve are semantically related. You can use "Butterfly" instead a noun phrase "Throttle valve".