Formal:
* दोपहर का भोजन (Dopahar ka bhojan): This is the most common and formal way to say "lunch". It literally translates to "food of the afternoon".
Informal:
* लंच (Lunch): This is the most casual and widely understood way to say "lunch", as it's directly borrowed from the English word.
* खाना (Khana): This simply means "food", and it's often used to refer to any meal, including lunch. You can also use it in a sentence like "Khana kha lo" (Eat your food).
To ask someone if they want lunch:
* क्या आप दोपहर का भोजन करना चाहेंगे? (Kya aap dopahar ka bhojan karna chahenge?): This is a polite and formal way to ask someone if they'd like to have lunch.
* लंच करना है? (Lunch karna hai?): This is a more casual way to ask.
The best choice for you will depend on who you're speaking to and the setting.