Selamat pagi  'Good morning'

Selamat tengah hari 'Good day'

Selamat petang 'Good afternoon'

Selamat malam 'Good night'

Once again we see selamat interacting with other words, in this case times of the day. Pagi is morning, malam is night, petang is afternoon (maybe 3-7PM), tengah hari is middle [of the] day = noontime.

These four greetings are the typical way to start a conversation, in much the same way conversations can begin in the US with Good morning.

Apa khabar? 'What [is the] n...

Selamat Datang "Welcome"

Selamat is the word that starts most greetings. It's like "good" in Good morning.

Selamat means safe. So literally it means something like:

"Let there be safety in..."

Datang means come

So "Let there be safety in your coming" = 'Welcome'

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We looked at another word yesterday  tak 'not or no'

So we could say about a guy named Ben:

Ben tak datang ke kelas

'Ben didn't come to class'

Or We could say

Matt datang ke kelas

'Matt came to class'...