Particle ЛИ

One of the most "popular" mistakes made by foreign students is the expression of indirect question through calquing the grammatical structure fr om their native language. Even if you know the rules, you can instinctively get the following form with the required word "если" [ehsli] (whether/if).

INCORRECT:
Я спросила друзей, если мы поедем в Европу летом - I've asked my friends whether we go to Europe in simmer.
Я интересуюсь, если русский язык сложный - It's interesting to me whether the Russian language is diffucult.
Я узнаю у гида, если мне нужно рано вставать - I will ask my guide whether I have to get up early.

There is the particle ЛИ [li] (whether/if) for such phrases in the Russian language. We put it not after comma but after the word which lies at the heart of an ex * pression (question). Pay attention, there is no interrogative word in indirect questions ("когда" [kagda] - when, "где" [gde] - wh ere, "насколько" [naskol'ka] - how much, "почему" [pachimu] - why and so on).

The position of the particle "ЛИ" [li] is always the same not depending on what part of speech or construction we've used in a reported question in order not to use question with interrogative word (pay your attention to the examples). As for part of the speech, it can be a verb, construction with infinitive, adverb or adjective.

Он поинтересовался, люблю ли я пиццу - It was interesting to him whether I like pizza.
Друг спросил, собираешься ли ты на рыбалку - Friend has asked if you go fishing.
Я хочу знать, должен ли я купить рабочую тетрадь - I want to know whether I have to buy a copybook.
Они спросили, пойдём ли мы ужинать в ресторан - They've asked if we go fishing.
Мама спросила, достаточно ли у нас денег - Mom has asked if we have enough money.
Учитель спросил, понятно ли нам задание - Teacher has asked whether we understand the task.
Сестра поинтересовалась, хорошая ли погода в нашем городе - My sister has asked whether we have good weather in our city.
Мы спросили, дорогие ли билеты в театр - We've asked if the theater tickets are expensive.