Grandfather clock and Pendulum clock

Grandfather clock noun - A pendulum clock enclosed in a tall narrow case.

Pendulum clock and grandfather clock are semantically related. In some cases you can use "Pendulum clock" instead a noun phrase "Grandfather clock".

Pendulum clock noun - A clock regulated by a pendulum.

Grandfather clock and pendulum clock are semantically related. Sometimes you can replace phrase "Grandfather clock" with "Pendulum clock", this phrases are similar.