The reserved words in R's parser are
if
else
repeat
while
function
for
in
next
break
TRUE
FALSE
NULL
Inf
NaN
NA
NA_integer_
NA_real_
NA_complex_
NA_character_
…
and ..1
, ..2
etc, which are used to refer to
arguments passed down from a calling function, see ...
.
Reserved words outside quotes are always parsed to be
references to the objects linked to in the ‘Description’, and
hence they are not allowed as syntactic names (see
make.names
). They are allowed as non-syntactic
names, e.g.inside backtick quotes.