The two adjectival forms:
- geometric, electric
- geometrical, electrical
But the 2nd form is closer towards forming adverbs
- geometrically, electrically
Some words skip the 1st form altogether, so that these words are not used or rarely used
Some words tend to discourage the use of the 2nd form
Anecdotal evidence would indicate that statistically, empirically, or in most of the cases,
- the 1st form is directly adjectival, whereas,
the 2nd form is suggestive of the 1st, suggesting that the descriptee is like the 1st form.
- human behaviour vs human-like behaviour
- god vs god-like
- human vs humanoid
- cube vs cuboid
the 2nd form denotes attributes or activities pertaining to the 1st form
- the 2nd form casts a wider net, such that the 1st form is a subset of the 2nd. There are situations which you could use both forms as adjectives, but there are situations where only the 2nd form would be precise.
1st form being subset of 2nd
- If we wanted to describe a drawing that conforms to the precision of geometry, we could use
either geometric drawing or geometrical drawing.
OTOH, for a drawing that associates or prescribes geometry, without itself being constrained to the precision of geometry, we would use
We have a geometrical chart listing all the geometric shapes produced in the factory.
There would be less clarity, in saying
We have a geometric chart listing all the geometrical shapes produced in the factory.
For example, electric vs non-electric:
- We could say either electric vehicles or electrical vehicles, though we normally avoid the 2nd form to describe electric vehicles.
- However, if we need to denote two "non-electric" vehicles, where one whose combustion and monitors are sustained or facilitated by electricity, versus the other which is sustained by mechanical contraption we could refer to them as the electrical vehicle, versus the non-electrical vehicle.
Or we could use a mouthful to describe the first car as "the
electrically facilitated-combustion car with electrical switches for
lighting and music, with electrical dashboard of electrical
speedometer and odometer, with electrical seat warmers, electrically extendable antenna, etc".