A list of steps cannot tell you what a tea is
Take two teas and list what was done to each. The first was plucked, heated, worked into shape and dried. The second was plucked, worked into shape, left alone for some hours, and dried. Those descriptions are almost identical, they are both accurate, and they describe a green tea and a black tea — two products with no flavour, no colour and no brewing behaviour in common. The difference is not in the list. It is in where the heat sits relative to the working of the leaf, and in what the leaf was allowed to do in between. This is why a catalogue that tags a tea with its processing methods and stops there has not said anything useful. TeaHQ stores each tea's processing as an ordered array rather than as a set of tags, and stores the routes themselves as ordered records, precisely because the order is the information. Reordering the tags would not change a set; it changes a tea completely.
The one comparison that carries most of the subject
Green tea heats the leaf before anything ruptures it. Black tea ruptures the leaf and never heats it until the drier. That is the whole of it, and everything a drinker notices follows. Heat first means the enzymes are gone before there is anything for them to act on, so the leaf stays green, the cup stays fresh and vegetal, and no malt or dried-fruit character can develop because the chemistry that produces it was shut down in the first minutes. Rupture first means the enzymes meet their substrates in air and are given hours, so the leaf browns through, the liquor turns red, and the compounds that give body and stand up to milk are built. Same plant, same shoot, same operations, opposite order. Nothing else in tea explains as much for as little effort, and it is worth holding onto because every other category is a variation on this one axis: oolong applies the heat in the middle and only after damaging the leaf at its edges, white tea never ruptures and never heats, yellow tea heats first like a green tea and then adds a step.
Three shapes of difference, and they are not the same shape
Once you look at routes rather than at steps, the differences between them fall into a small number of kinds and it is worth being able to tell them apart. A REORDERING keeps the operations and moves them: green against black. A SUBSTITUTION keeps the shape and changes what fills one slot: steam instead of a hot pan gives Japanese green tea instead of Chinese; a cutting machine instead of a twisting one gives CTC instead of orthodox; sun instead of an oven at the drying slot gives a pu-erh that will change for decades instead of a green tea that will go stale. An INSERTION adds an operation and changes nothing else: yellow tea is a Chinese green tea with a smothering step between the fixation and the finishing bake. And an OMISSION removes one: matcha's route is the sencha route with the rolling left out, and white tea's route omits both the fixation and the rolling. Those four are not stylistic descriptions; they behave differently. Substitutions propagate backwards — put CTC rollers in a factory and the wither has to change, and eventually the harvesting does too. Omissions are one-way: a route can always decline to roll a leaf and no route can un-roll one.
Why order beats duration, and why numbers are scarce here
The obvious objection is that timing matters too — that a two-hour wither and a twelve-hour wither are different things — and it does. But duration is a variable inside a step and order is a fact about the route, and the two behave differently under uncertainty. Duration depends on the cultivar, the intake, the weather, the altitude and the factory: an oxidation that takes three hours in a hot lowland factory takes far longer at altitude for the identical result, and a figure copied from one to the other is worse than no figure. Order does not vary that way. Every orthodox black tea in the world rolls before it dries, everywhere, in every season. So the durable, transferable knowledge in tea processing is structural, and the numbers people most want are the ones least worth quoting. This is also why TeaHQ's route records carry no temperatures and no times. It is not squeamishness about detail; it is that the detail is real and specific to a batch, and the structure is real and general.
What this buys you in a shop
The number of tea names is effectively unbounded and new ones appear every season. The number of operations is about a dozen and has not changed in living memory. A drinker who has memorised names can recognise the teas they have met; a drinker who can read a route can place a tea they have never heard of, from the leaf, the liquor and two sentences on the back of a packet. That is the whole practical argument for learning the sequence rather than the catalogue. It also makes the vocabulary problems visible rather than confusing. When a packet says fermented, knowing where in a route microbial fermentation could possibly sit tells you immediately whether the word is being used correctly or is a translation of the Chinese word for oxidation. When a seller describes a partly oxidised oolong as half-way between green and black, knowing that oolong is oxidised at the leaf margin and barely at all in the centre tells you the description is a convenient fiction rather than a measurement.