The difFerence between THESE words !

'Respond ' could also mean to react ,this reaction could be a verbal reply or just an action . He responded to her email quickly by calling her on the phone . He responded to her email quickly by only 2 words " me too " . research/investigate in both cases you do examine , inquire , try to find out about something in a systematic manner , yet 'to investigate ' is more concerned with allegations, accusations, detection of crimes etc ... The research is more associated with scientific issues . In fact they are still used in both fields interchangeably He kept researching the close relationship between the 2 phenomenas for more than 2 years. He investigated the case to decide ,whether there is enough evidence for the crime or not . inquire /look into They could mean the same. To inquire is also to ask for information about something from a certain source, it also means to look into and investigate . I hope this helps a bit. In fact as much as those verbs do intersect at a point ,where they have the same meaning , as much as they could have different meanings and won't be interchangeable in certain contexts .

Question and wonder could have completely different meanings ,what doesn't make them comparable in that case , in one sense they could be comparable ,because they have then similar meanings . Question in the sense of doubting and speculating ,here it is very much like 'to wonder ' in the sense of to think curiously ,to doubt about something or someone, to desire to know something . In this case they are both reflecting the same meaning,but to use them interchangeably you will have to modify the sentence structure as follows : He wondered about the origin of this proverb. He questioned the origin of this proverb. Discuss/ Debate To discuss a matter or a subject is to talk about it and converse with a person or a group of people . to debate is to argue about something . It involves a discussion ,but not without some pros and cons and different point of views. Debate is more commonly used in a formal manner ,it is more structured and longer than a discussion. They discussed the matter over lunch. They debated about the possibility of merging the 2 companies and didn't come to an agreement at the end. respond vs reply They could be interchangeable in many contexts . To reply is more of an answer to a question or inquiry , while responding could be to a question or an action . She replied to the complain letter by apologizing and promising to render better service in the near future. She responded to the complain ........( the same applies).