Night sky darkens.

Meaning: This means that the night sky is becoming darker. It's like saying, The sky is getting darker as night falls.

Choice of Words: Night is the period of time between sunset and sunrise. Sky is the area above the Earth that is visible from the ground. Darkens is a verb that means to become dark or black. In this context, it means the night sky is becoming darker.

Alternative Expressions

The sky gets dark at night.

Meaning: This means that the sky turns dark when it is night time. It's like saying, The sky becomes dark when the sun goes down.

Choice of Words: Sky means the big, blue thing you see above you. Gets means becomes or turns into something. Dark means without much light. Night means the time of day when it is dark outside. When you put them together, "The sky gets dark at night" means that the sky becomes dark when it is night time.

The sky turns black in the evening.

Meaning: This means that the sky becomes black after the sun has set. It's like saying, The sky becomes black after the sun goes down.

Choice of Words: Sky means the big, blue thing you see above you. Turns means changes to something else. Black means the darkest color. Evening means the time of day just after the sun has set. When you put them together, "The sky turns black in the evening" means that the sky changes to black after the sun has set.

The sky becomes dark after sunset.

Meaning: This means that the sky becomes dark after the sun has set. It's like saying, The sky becomes dark when the sun goes down.

Choice of Words: Sky means the big, blue thing you see above you. Becomes means changes to something else. Dark means without much light. Sunset means the time of day when the sun goes down. When you put them together, "The sky becomes dark after sunset" means that the sky changes to dark after the sun has set.

Related Expressions