countability - Is experience countable or uncountable?

"Seeing the Grand Canyon was certainly____(an /some) experience." Is experience countable or uncountable? Should I use some or an?

Answer

In some instances, it's countable and in other uncountable, depending on its meaning. According to the Longman dictionary if it means "something that happens to you or something you do especially when this has an effect on what you feel or think", it's countable.Seeing the grand Canyon, of course, has a great effect on everybody, so in this case it's countable and you should say: "Seeing the Grand Canyon was certainly an experience". More examples:

Ballooning is quite an experience.

I have a lot of experiences from trip to Africa.

Seeing the Grand Canyon was a really fantastic experience.

But if it means "knowledge or skill that you gain from doing a job or activity", it's uncountable.