Most of the time ‘and‘ is not an important word in a sentence, so we don’t stress it. We usually say /ən/.
When it is important, we stress it. We say /ænd/.
The question is…when is it important?
The answer…when we want to emphasize that we want both or all of something.
“Do you want a red umbrella or a blue one?”
[The question assumes you will pick only one color.]
“I want a red one and a blue one.”
[You really want both.]
The optometrist asks you:
“Are you here for sunglasses or regular glasses?”
“I’m getting sunglasses and regular glasses.”
“What do you think? Should we get a cat or a dog?”
“I want a cat and a dog.”
“I heard that this restaurant is only open for dinner.”
“No, this restaurant serves breakfast, lunch and dinner.”
“Are you going to get soup or a sandwich?”
“I’m getting soup and a sandwich, and some potato chips.”
“Do you need euros or dollars?”
“I need euros anddollars.”
“Are you really going to have time to do all those things on your vacation?”
“I sure am. I’m going skydiving, bungee jumping, hiking, and surfing.
Why don’t you come with me?”