Easy way to remember kolacja
As the Tips and Notes indicate, "kolacja" is only translated as "dinner" in English because of the time of day it is eaten. It is not the main meal. We actually have such a word in English however: "collation: a light, informal meal." This makes the Polish word much easier to remember for me.
Not necessarily. A supper is a light evening meal. However, most of the English-speaking world has the main meal in the evening so that we have "lunch" around noon and "dinner" in the evening. That isn't true in the southern United States where the tradition is to have "dinner" at noon and "supper" in the evening, which seems to be the Polish tradition as well. So if you're not in the southern U.S., "supper" might sound a little strange but it would certainly be understood and to speak of "dinner" at noon would leave them a little confused.
To jest kolacja, a na kolacje bedziemy jesc kanapki (this is a dinner, and for dinner we will eat sandwiches).
Mianowni (kto?co?): to jest kolacja (this is a dinner) Dopelniacz (kogo?czego?): nie ma kolacji( there is no dinner) Celownik (komu?czemu?): przygladam sie kolacji (I am looking at dinner) Biernik (kogo?co?): widze kolacje (I see dinner) Narzednik (z kim? z czym?) z kolacja (with dinner) Miejscownik (o kim? o czym?) o kolacji (about dinner) Wolacz (!) kolacjo ( dinner!)
forms of polish noons change depending how they are used in sentence (see grammar).
Everything here is about cases. "kolacja" is Nominative - it's the basic form of the noun, the one that you will find in dictionaries. "kolację" is Accusative - it's one of the most important cases, needed by a lot of common verbs, such as "widzieć" (to see): "On widzi kolację" or "jeść" (to eat): "Ja jem kolację".
If the notion of cases confuses you, take a look at this post and look at some links in the "Cases" section. They are absolutely crucial to Polish, without cases nothing makes sense.