This puzzle is based off the What is a Word™ and What is a Phrase™ series started by JLee and their spin-off What is a Number™ series.
If a word conforms to a certain rule, I call it an Eternal Word™. Use the following examples to find the rule:
$$ % set Title text. (spaces around the text ARE important; do not remove.) % increase Pad value only if your entries are longer than the title bar. % \def\Pad{\P{0.0}} \def\Title{\textbf{ Eternal }} % \def\S#1#2{\Space{#1}{20px}{#2px}}\def\P#1{\V{#1em}}\def\V#1{\S{#1}{9}} \def\T{\Title\textbf{Words}^{\;\!™}\Pad}\def\NT{\Pad\textbf{Not}\T\ }\displaystyle \smash{\lower{29px}\bbox[yellow]{\phantom{\rlap{rubio.2019.05.15}\S{6px}{0} \begin{array}{cc}\Pad\T&\NT\\\end{array}}}}\atop\def\V#1{\S{#1}{5}} \begin{array}{|c|c|}\hline\Pad\T&\NT\\\hline % \text{ASKING}&\text{ANSWERING}\\ \hline \text{ATARI}&\text{KONAMI}\\ \hline \text{NINTENDO}&\text{SEGA}\\ \hline \text{ASTEROIDS}&\text{PACMAN}\\ \hline \text{RACHEL}&\text{MONICA}\\ \hline \text{CHANDLER}&\text{PHOEBE}\\ \hline \text{PINK}&\text{FUCHSIA}\\ \hline \text{MAGENTA}&\text{LAVENDER}\\ \hline \text{EARTH}&\text{PLUTO}\\ \hline \text{DWARF}&\text{MIDGET}\\ \hline \text{PLANET}&\text{PLANETOID}\\ \hline \text{70}&\text{69}\\ \hline \text{PROPER}&\text{IMPROPER}\\ \hline \text{FACTORY}&\text{FACTOR}\\ \hline \text{FLATTER}&\text{FATTER}\\ \hline \end{array}$$
The puzzle satisfies the series' inbuilt assumption, that each word can be tested for whether it is an Eternal Word™ without relying on the other words.
These are not the only examples, there are more of both Eternal Words™ and Not Eternal Words™.
CSV version:
ASKING, ANSWERING ATARI, KONAMI NINTENDO, SEGA ASTEROIDS, PACMAN RACHEL, MONICA CHANDLER, PHOEBE PINK, FUCHSIA MAGENTA, LAVENDER EARTH, PLUTO DWARF, MIDGET PLANET, PLANETOID 70, 69 PROPER, IMPROPER FACTORY, FACTOR FLATTER, FATTER
