Many people now treat the Chinese term 息灭 as a mistake. It is not in the dictionary, and it was never taught in the Chinese language syllabus from primary through high school. If the word does not exist, then the sound xīmiè can only belong to 熄灭. Yet there are contexts where 息灭 is exactly the word needed: '周朝时很多诸侯息灭'—many feudal states of the Zhou dynasty perished—or '因为环境变迁很多物种息灭'—many species went extinct because their environments changed. In these sentences the 息 is the same as in 生生不息: it refers to continuity, transmission, or a line of descent. Once 息灭 is classified as an error, that meaning becomes difficult to express precisely. 熄灭 is not an adequate substitute.
The distinction is straightforward. 息灭 means extinction, usually of a state, a people, or a species. 熄灭 means that an object is no longer burning. 息灭 belongs with lineage, culture, and species; 熄灭 belongs with fire. The burning or fire sense of 熄灭 can be extended to hope or desire, but it cannot be extended to lineage, culture, or species, because those have nothing to do with combustion.
Behind this simple pair lies a cultural problem worth thinking about. As society changes, characters and words with similar meanings get merged. Some are retained and their meanings expand; others are dropped. The advantage is that later learners have less to learn. The disadvantage is that in some situations the language becomes less precise.
Dictionaries and school syllabi are adjusted continuously and serve as norms. This is not necessarily in conflict with reading older inherited works: a new norm governs usage after it appears, not the past. But a real contradiction arises. Suppose that after a new norm takes effect, someone needs a word that is absent from the norm but has long been in use. Can that older word be defined as wrong, and is it necessary to define it that way? In language teaching, exams, and academic writing, this matters a great deal, because it directly affects how work is scored.
If such usage is judged wrong, cultural transmission suffers a break. People who regularly study classical texts cannot easily sort high-frequency words into those inside the new norm and those outside it; the inconvenience is considerable. In many situations, two distinct words also make expression more accurate. Forcing several words into one can leave no suitable word at all. This happens often when dialect terms or expressions from Hong Kong and Taiwan are converted into standard written Chinese: a simple word may need a whole sentence to explain, or it may be replaced by a term that invites ambiguity.
If such usage is judged acceptable, language teaching and related work face difficulties. Teachers may have received training only within the new norm and may not have broadened their knowledge beyond it, while the syllabus gives them a specific body of content. Expanding that content adds to their burden.
The wider question is whether culture should be assigned a fixed boundary. What lies inside the boundary is certainly correct; what lies outside may be correct in research but wrong on an exam. Culture is vast, and it is precisely this vastness that demonstrates the length of its inheritance. Every country and people wants its culture to be broad and deep. But the broader and deeper a culture is, the harder it is to learn and transmit. For the sake of learning and transmission, a vast culture has to be simplified. That is the internal dilemma of a broad cultural inheritance.
Simplification is meant to remove the weeds and keep the essence, but in practice it is hard to tell them apart—or rather, there is too much that counts as good and too little agreement on what to discard. Even a weed is not entirely useless. Foxtail grass, once treated as a nuisance, is now planted widely in parks. Standards change with time, and so do judgments about what is good and what is weed. A temporary choice, however, can cause a permanent loss.
How to choose is difficult, perhaps unsolvable. My own view is that when a choice is this hard, the discarded part should not be labeled wrong. It should be labeled uncommon. In education and in settings that require grading, there should be more open-ended questions and fewer closed questions that demand a single right or wrong answer. How to ensure consistency in judging open-ended questions is a separate problem. I do not know enough to say much about it.
The grass may have another botanical name. To me it looks like an oversized foxtail. My knowledge is limited, so corrections are welcome.