Basic Conversations
hola is a common way to greet someone hola means hello or hi
buenos is only used with días so it would be buenos dias and this means good morning.
the other two (good evening and good night)
both start with buenas, so its buenAs not buenOs
good evening is buenas tardes
good night is buenas noches
here is a site to provide you with more info on greetings:
http://http://www.lingolex.com/swom/wom-greetings.htm
