Proportion is about balance and how things fit together harmoniously. For example "That hound dog's tiny legs look out of proportion to that big fat body."
The prefix comes from the Latin pro meaning "on behalf of, for." If you're Proportion likes portions, and for them to be the right size. The cake's sweetness is in direct proportion to how much sugar you put in. It's a compliment to tell someone he or she has just the right proportions, but you might get slapped. It can also be a part of something, as in a significant proportion of our student body has dyed their hair purple.
Definitions of proportion
1
n the relation between things (or parts of things) with respect to their comparative quantity, magnitude, or degree
“an inordinate
proportion of the book is given over to quotations”
“a dry martini has a large
proportion of gin”
 Synonyms:
 ratio
 Type of:

magnitude relation, quantitative relation
a relation between magnitudes
n the quotient obtained when the magnitude of a part is divided by the magnitude of the whole
 Types:
 show 12 types...
 hide 12 types...

casefatality proportion
the number of cases of a disease ending in death divided by the number of cases of the disease; usually expressed as a percentage or as the number of deaths per 1000 cases

casetoinfection proportion, casetoinfection ratio
the number of cases of a disease divided by the number of infections with the agent that causes the disease

content
the proportion of a substance that is contained in a mixture or alloy etc.

rate
a quantity or amount or measure considered as a proportion of another quantity or amount or measure

scale
the ratio between the size of something and a representation of it

golden mean, golden section
the proportional relation between two divisions of line or two dimension of a plane figure such that short : long :: long : (short + long)

pct, per centum, percent, percentage
a proportion in relation to a whole (which is usually the amount per hundred)

batting average
(an extension of the baseball term) the proportion of times some effort succeeds

absentee rate
the percentage of workers who do not report to work

occupancy rate
the percentage of all rental units (as in hotels) are occupied or rented at a given time

vacancy rate
the percentage of all rental units (as in hotels) that are unoccupied or not rented at a given time

unemployment rate
the percentage of the work force that is unemployed at any given date
 Type of:

quotient
the ratio of two quantities to be divided
n balance among the parts of something
 Synonyms:
 symmetry
 Antonyms:

disproportion
lack of proportion; imbalance among the parts of something
 Type of:

balance, counterbalance, equilibrium, equipoise
equality of distribution
n harmonious arrangement or relation of parts or elements within a whole (as in a design)
 Synonyms:
 balance, proportionality
 Type of:

arrangement, placement
the spatial property of the way in which something is placed
v adjust in size relative to other things
 Types:

scale down
reduce proportionally

scale up
increase proportionally