1. "ch" is often substituted for "gh";
2. "mb" is often represented by "m" or "mm"
3. "th" is sometimes represented by "d" or "dd"
4. initial "h" is frequently dropped
5. "ng" is often represented by "m"
6. "quh" is equivalent to "wh"
7. initial and final "sh" appears as "s" in stressed syllables
8. a final "d" appears as "t"

ane a, one
ay always
but, bot without, but, unless, only, lacking, except
can does or did; to be able or to know
couth, coud, could, cowd, cowth, culd often "did"; as a verb, "was able"
eik, eke also
gar, gart, ger, garris make, do, help (modal), cause
gif, giff, gife, geve, gyf often "if"; as a verb, forms of "give"
man, mon, mone must
quha who, whoever, if anyone
quhair, quhar, quhare where, wherever, in which, when
quhen when, whenever, as soon as
quhile, quhill, quhyle, quhyll a time, a short time, until, while, as long as
quhilk, quhylk, quhilkis, quhilks which, who, whom, what, whoever
sa, so, sua, swa so, thus
syne, sen then, since, therefore, afterwards
the often read as "thee"
thir these
till until, to, for

Notes adapted from:

The Poems of Robert Henryson
Edited by Robert L. Kindrick
Originally Published in The Poems of Robert Henryson
Kalamazoo, Michigan: Western Michigan University

http://www.lib.rochester.edu/camelot/teams/henryint.htm