Answer:
Possibly the word most commonly said before taking a sip
You fill it and it empties, A metaphor for plenty, Depending on what half you see, It's either full or empty
Mouth up it gets filled, mouth down it gets empty.
People in love are often bound to this.
Bobby likes Jimmy but not Joe, apples but not pears, jeeps but not vans, shinny but not hockey, tennis but not squash. Who will he like, Sara or Sally?
Cycle Cycle Cycle.
Easy
Animal
Difficult
Food
Funny
Kids
Logic
What am I?