They are totally different concepts! 'Clean' (the adjective) means 'not dirty'. If the floor needs to be cleaned, this means that it has dirt, mud, footprints or coffee stains on it. You need to get a mop and a bucket of hot soapy water to clean the floor. 'Tidy' (the adjective) means 'neat'. This refers to the organisation of objects. If you tidy your desk, you this means that you organise it. You throw away any objects that you don't need, put away other things in drawers, and arrange the remaining objects neatly - pens in pen pot, papers in a neat pile and so on. PS Here's a bonus verb: Many learners also confuse the verb 'clean' and 'clear'. 'Clear' means to remove all the objects, usually for a particular purpose. For example, when an employee is fired, they would be asked to clear their desk (take all their belongings), ready for the next person to take over that desk.

Tidy means to put things visually in order. Clean suggests more hygiëne. The house can be tdy, but there is still dust and dirt . Tidy your desk,... all the pictures, plants and papers may be attanged nearly, and to clean your desk, you would leave an empty surface.