Use of the word Salat

I am currently learning new vocabulary regarding foods, and the word Salat is confusing to me. The words salad and lettuce in English appear to be the same in German, i.e. Salat. So how would I order in a restaurant "a salad with tomatoes, cucumbers and lettuce"? Would I say, "einen Salat mit Tomaten, Gurken und Salat" or "einen Salat mit Tomaten, Gurken und Salatblätter"? Is the meaning of the word (salad vs. lettuce) understood simply by context? 
Thanks to anyone in advance for the clarification! 

Hi PaulS108,

you are right, the word Salat can be used to describe both the prepared meal (salad) and the vegetable (lettuce) depending on the context. For example:

In a restaurant you could say:
"Ich hätte gerne einen gemischten Salat mit Tomaten und Gurken bitte." - "I would like to have a mixed salad with tomatoes and cucumbers please."

In a supermarket you could say:
"Ich hole etwas Spinat, Knoblauch und Salat aus der Gemüseabteilung." - "I'll get some spinach, garlic and lettuce from the veggie department."

Hope this helps.

Tschüss,
Julia