Interesting, NicholasW...I never thought of the dropping of the "e" for the --ing suffix, in the case of aging/ageing, as being a US/UK variation until your mention of it. Is this the case in anyone else's experience? And why, Nicholas, does it stand out to you as an Americanism in this particular word and not the others where the "e" is dropped? And is there any early English rule (or tenet), perhaps, that states that one form should be favored over the other when both are acceptable...or outlines a preference for certain situations?