Jam, not jelly; jelly, not jello. I agree with blackmage_nuke.

Also:
Football, not soccer
Scones, not biscuits
Subway sub, not subway sandwich
Chicken burger, not chicken sandwich
Toilet, not potty
Soft drink, not coke/soda/pop
Motorway, not freeway/highway
Footpath, not sidewalk/pavement
Lounge, not den
Paracetamol, not tylenol/acetominophen
Bonnet, not hood
Boot, not trunk
AuminIum, not aloominum
Nissan, not NEESAHN
Hyundai, not HUNDAY
Mazda, not MARZDA