This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.
If a word conforms to a special rule, I call it a Written Word™.
Use the following examples below to find the rule.
$$ % set Title text. (spaces around the text ARE important; do not remove.) % increase Pad value only if your entries are longer than the title bar. % \def\Pad{\P{2.0}} \def\Title{\textbf{ Written }} % \def\S#1#2{\Space{#1}{20px}{#2px}}\def\P#1{\V{#1em}}\def\V#1{\S{#1}{9}} \def\T{\Title\textbf{Words}^{\;\!™}\Pad}\def\NT{\Pad\textbf{Not}\T\ }\displaystyle \smash{\lower{29px}\bbox[yellow]{\phantom{\rlap{rubio.2019.05.15}\S{6px}{0} \begin{array}{cc}\Pad\T&\NT\\\end{array}}}}\atop\def\V#1{\S{#1}{5}} \begin{array}{|c|c|}\hline\Pad\T&\NT\\\hline % \text{ GOOD }&\text{ BAD }\\ \hline \text{ JANUARY }&\text{ DECEMBER }\\ \hline \text{ HAPPY }&\text{ SAD }\\ \hline \text{ JOKER }&\text{ CLOWN }\\ \hline \text{ GRAVEYARD }&\text{ GRAVE }\\ \hline \text{ HYPER }&\text{ SUPER }\\ \hline \text{ EIGHT }&\text{ SEVEN }\\ \hline \text{ EGYPT }&\text{ ISRAEL }\\ \hline \text{ POLICEMAN }&\text{ FIREMAN }\\ \hline \text{ QUINTET }&\text{ TRIO }\\ \hline \end{array}$$
And, if you want to analyze, here is a CSV version:
Written Words™,Not Written Words™
GOOD,BAD
JANUARY,DECEMBER
HAPPY,SAD
JOKER,CLOWN
GRAVEYARD,GRAVE
HYPER,SUPER
EIGHT,SEVEN
EGYPT,ISRAEL
POLICEMAN,FIREMAN
QUINTET,TRIO