I'm still puzzled about the use of σαν and οπώς. I'd be obliged if any Greek speakers could give an example of a sentence or two where you could use οπώς but never σαν, and similarly where you would use σαν but not οπώς.
Όπως is "like, as, such as". Σαν is "like, as though" and σαν +subjunctive is "as if". Σαν can also be used with the meaning of "upon" (in the time sense). *Upon hearing the news, he smiled"="Σαν άκουσε τα νέα, χαμογέλασε"
More extensivelly: Όπως is used for similes (and σαν). He lives like a king=ζει σαν βασιλιάς, ζει όπως (ζει) ένας βασιλιάς. Do it like John=Κάνε το όπως (το έκανε) ο Τζον, κάνε το σαν τον Τζον. If a verb follows, όπως must be used and not σαν, unless the verb is in subjunctive where only σαν can be used (and expresses a non real simile, same as "as if") Μιλάει σαν να ήταν πρωθυπουργός=He speaks as if he were a president. You can't say Ζει σαν ζει ένας βασιλιάς, it's completely wrong (with the meaning of as, like, but you can with the meaning of upon, as described before). Also όπως must be followed by article (indefinite or definite, and nominative case). Σαν does not have to be followed by an article if it expresses a generic meaning (lke the king example above) and if you want to make a specific simile, you have to add a definite accusative article. He speaks like his brother=Μιλάει σαν τον αδερφό του, μιλάει όπως ο αδερφός του.
October 8th 2017: ντομάτα is still not accepted, though it's the standard word used by Greeks.
Would this be used when we say in English "his face was red as a beet", meaning "he was embarrassed".
In the audio exercise, I hear ντομάτα rather than τομάτα - am I right?
(Δτομάτα was accepted as a secondary answer but I want to check if my ear is tuned right!)
I think you're right it does sound like "d" /"ντ". That's because when the tree was first created some years ago the main usage was "ντομάτα". In the new tree we'll have "τομάτα" with "ντομάτα" as an alternative, but the audio will only have the main usage. Thanks for the heads up.