Longman Dictionary of Contemporary English - this

~1 determiner plural these 1 used to talk about a person, thing, idea etc that has already been mentioned or that the person you are talking to already knows about  (Wait till you hear this joke. | What is the purpose of your visit to this country? | There will be another meeting later this week. | How can we help these poor children? | If we carry on at this rate we'll be bankrupt by the end of the week.) 2 used to talk about the person or thing nearest to you or the time that is soonest etc  (I'm going to visit my Mum this Wednesday. | I'll look in these rooms if you look in all the rest. | I'm surprised you like that photo - I prefer this one.) 3 spoken used in stories, jokes etc when you mean a person or thing, especially when you do not know their name  (When am I going to meet this boyfriend of yours? | I met this really weird guy tonight.) 4 this minute/second immediately  (I want to see you in my office this minute!) ~2 pronoun plural these 1 used to talk about a person, thing, idea etc that has already been mentioned or that the person you are talking to knows about already  (Where did you find these? | This is terrible. What on earth are we going to do? | If you think that's funny wait till you hear this.) 2 used to talk about the person or thing nearest to you, the time that is soonest etc  (These are your coats, aren't they? | That might be a much prettier dress but I feel more comfortable in this.) 3 a) informal used to introduce someone to someone else  (Sam, this is my sister, Liz.) b) used when you have answered the telephone and you want to give your name  ("Can I speak to Joan please?" "This is Joan speaking.") 4 a particular time  (I thought he would have been back before this. | Well young lady, what time do you call this?) 5 this, that and the other also this and that especially spoken various different things, subjects etc  ("What have you two been gossiping about all evening?" "Oh this, that and the other.") 6 what's (all) this? spoken used to ask what is happening, what someone's problem is etc  (What's this? Crying again?) ~3 adv + adj/adv this big/many etc spoken used to say how big or how many, especially because you are showing the size, number etc with your hand  (this big/tall etc)  (The table's about this high and this wide. | this much/many)  (Do you know he cut this much off my fringe without even asking me!)