equal straight 5 realizations
ACCEPTED Realization 1
type Polysemy
language Classical Arabic
lexeme تَعَدَّلَ taʕaddala
meaning 1 it became, or was rendered, straight, or even
direction
meaning 2 to be equal taʕaddalat ḳīmat-u l-matāʕ-i bi-kad̲ʕ
the value of the commodity was equal to such a thing
reference Lane: 1973
comment

V stem from عَدَلَ meaning 1) to be fair, righteous, just; 2) to decline, deviate. 

ACCEPTED Realization 2
type Polysemy
language Croatian
lexeme ravan
meaning 1 equal ravan geniju, ravan nuli
equal to genius, equal to zero
direction
meaning 2 straight
reference HJP
comment
ACCEPTED Realization 3
type Internal cognates
language Russian
lexeme 1 равный
lexeme 2 ровный
meaning 1 equal
direction
meaning 2 straight
reference <personally collected data>
comment
ACCEPTED Realization 4
type Polysemy
language Serbian
lexeme раван (ravan)
meaning 1 equal бити раван оцу (с оцем) по храбрости
to be equal to his father in courage
direction
meaning 2 straight у равној линији
in a straight line
reference Vujanitsh et al. 2007: 1100
comment
NEW Realization 5
type Polysemy
language Tamil
lexeme cemmai
meaning 1 equality
direction
meaning 2 straightness
reference Fabricius Tamil: 437
comment

It seems that this binary polysemy pattern is a part of different larger pattern, in comparison with other realizations of this shift: 

other meanings of this lexeme are: 1) excellence, dignity 2) redness, orange or gold colour.