We often say 'speak English' to refer to an ability or constant fact. For example: 'They speak English in New Zealand' or 'We're looking for a sales assistant who speaks English'. We say 'speak in English' to refer a choice of whether to speak in English or in another language on a particular occasion or in a particular context. "I saw some drunken British tourists behaving really badly and saying rude things about my town. They thought I couldn't understand when what they were saying, so they were surprised when I suddenly spoke to them in English and told them to go away." There is some overlap. For example, with your italki language partners, you might say 'Let's speak English together', because the purpose of your getting together is to practise the language: 'speak English' is your joint activity. Or you could say 'Let's speak in English together' (as opposed to speaking in another language). Here's some general advice: 1. If you're using the verb 'speak', and you're not sure whether it should be followed by 'in', I would advise you not to use 'in'. This is because 'speak in + language' may often be wrong. For example, it would be wrong to say 'New Zealanders speak in English' (as opposed to 'New Zealanders speak English'). However, it is rarely wrong to omit the 'in': I think you can pretty well always replace 'speak in English' with 'speak English'. 2. If you're using any other verb, you should use 'in'. For example 'I talked to her in English' or 'You need to answer in English' or 'They asked me a question in English.' I hope that helps.

"Do you speak English?" = I want to know whether you know English and are able to use it in a conversation "Do you mind if we speak in English?" = I'd rather have our conversation in English than in another language N.B. Hope this helps but let's wait for an aswer from a teacher, anyway

Speak English - обладать навыками, чтобы говорить по-английски. I speak English, so I understand you. Speak in English - разговаривать в беседе, в которой говорят на английском языке. His native language is Spanish, but he spoke those words in English, so that no one could understand him.

When you are talking about the languages you can speak, you don’t say “in”: I speak English, French, and Spanish. This means you have the ability to speak all three. I speak English. This means you have the ability to speak the language. You cannot say I speak in English if you mean you have the ability. You can use IN ENGLISH when you are talking about a certain case of speaking the language. If you say, I speak in English, that means you are using that specific language (rather than another language you know): She did not understand me when I spoke in French so I had to speak in English. When you have a choice of languages, you can say “in” or you can just say the language: I speak in English with my kids and in Spanish with my parents. OR I speak English with my kids and Spanish with my parents.

"Speak English". It's to emphasize someone's language ability. I would say that it has hidden (can). You speak a language. You speak English. I speak French. He speaks Spanish. She speaks Italian. What languages do (or can) they speak? "in English (or any language)" is an adverbial aspect, to provide more detailed description. For example, consider a sentence "He spoke to me", is a general statement, without stating where, how, when, or what content. He spoke to me yesterday. He spoke to me loudly and quickly. He spoke to me in his room. He spoke to me IN ENGLISH. He spoke to me about his mother. "IN English" is an adverbial aspect. Combining all these, you get a long descriptive sentence. He spoke to me yesterday in his room about his mother, in English, loudly and quickly. You can change "speak" to "say" as in "say in English", but you can't say "He says English". You have to say "He says in English".