Tenses: Present continuous tense with a period of time

LaboriousIf somebody says "I'm cleaning the house today", does it mean that they have already started to clean it, i.e., they are in the middle of doing it?

With no further context, we don't know whether the speaker has started the cleaning or has decided to do it later today. If s/he has started, we don't know whether s/he is actually cleaning at the moment

Thanks for your help, dear 5jj. I don't understand why the grammar sites give such definitions and examples without considering the ambiuities these examples could have. They don't say or mention anything of such ambiguities. I've been reading about the uses of present continuous tense, but after reading from various grammar sites I feel that I'm getting more and more confused with the appropriate

Few utterances have complete meaning without some form of context. If grammar books attempted to explain the precise meaning conveyed by a tense in every possible utterance, they would be thousands of pages long.

Virtually all uses of progressive forms denote limited duration in some way. Context will usually make it clear whether the action is/was/will be actually in progr

LaboriousMichelle is working in London this month. Does it give the listener the idea that Michelle is currently in London and is working there (for) this month?

The adverb and context are clues.
Today is June 2.
Michelle is working in London this month.
She started on June 1 and will continue until June 30.

Michelle is working today.

Thanks to both of you, teachers. Now it's much clearer to me. For example, if somebody says "I'm working on a new project this week" and If the week (this week) has already started or we are in the middle of the week, then this situatation of me working on a new project has already began, i.e, the working on a new project is in progress, though I may or may not be working on that project at the mo

LaboriousThanks to both of you, teachers. Now it's much clearer to me. For example, if somebody says "I'm working on a new project this week" and If the week (this week) has already started or we are in the middle of the week, then this situatation of me working on a new project has already began, i.e, the working on a new project is in progress, though I may or may not b

Laboriouswe can use the present continuous tense for an ongoing incomplete action that is being carried out during/over a limited period of time, not necessarily right now.

Right. With actions that are done sporadically, for example.

Sam is dating Louise. (But he is actually at work right now.)
Thomas is writing a book. (But he i

CalifJimSam is dating Louise. (But he is actually at work right now.)Thomas is writing a book. (But he is actually watching TV right now.)Karen is studying Russian. (But she is actually having breakfast right now.)The Smiths are remodeling their kitchen. (But they are actually at the movies right now.)

Thank you very much, teacher, for those useful examples. B

Laborioussomething continues or goes on over / during limited period of time

That's what the present continuous is communicating. You don't need a period of time. The use of the present continuous is telling you that it's happening over some period of time whether you say what the period is or not.

CJ