---
type: Object
title: Tea
description: An infusion brewed from the leaves of *Camellia sinensis* — the world's
  second most consumed beverage after water — whose white, green, oolong, black, and
  pu-erh forms differ only in how far the leaf is oxidized before drying.
tags:
- tea
- beverage
- botany
- oxidation
resource: raw/tea-guide.md
timestamp: '2026-07-16T15:54:42Z'
citadel_version: 0.3.0
---

Tea is one of the most widely consumed beverages in the world, second only to water in the total volume drunk each day.[^s1] In its strict sense, the word refers to an infusion prepared from the leaves of a single plant species.[^s2] That species is [Camellia sinensis](camellia-sinensis.md), an evergreen shrub native to the highlands of East and South Asia.[^s3] Beverages brewed from other plants — rooibos, chamomile, peppermint, or hibiscus — are properly called herbal infusions or tisanes; they are not tea in the botanical sense, however much they may resemble it in the cup.[^s4]

What distinguishes white, green, oolong, black, and pu-erh tea from one another is not the species of plant but how the harvested leaf is treated after picking.[^s5] The single most important variable is oxidation, the enzymatic process that begins when the leaf's cell walls are bruised or broken and its natural compounds react with oxygen in the air; by controlling how far this reaction is allowed to proceed before it is halted by heat, a maker can turn the same fresh leaf into radically different finished teas.[^s6]

The broad families fall along that oxidation spectrum.[^s7] White and green teas undergo little oxidation: white tea is barely handled at all, simply withered and dried, while green tea is heated early — by steaming or pan-firing — to deactivate the oxidising enzymes and lock in a fresh, grassy character.[^s8] Oolong tea is partially oxidized, occupying a wide middle ground, with lightly oxidised oolongs tasting floral and close to green tea while heavily oxidised ones approach the depth of black tea.[^s9] Black tea is fully oxidized, which develops its dark colour, brisk body, and robust flavour; in much of East Asia this category is known as "red tea," after the colour of the liquor rather than the dry leaf.[^s10][^s19] Pu-erh tea is fermented and aged: unlike the enzymatic oxidation of black tea, pu-erh undergoes microbial fermentation over months or years, producing an earthy, mellow brew that is often pressed into cakes and stored to mature.[^s11][^s18] A deeper look at how each family is made — including the yellow class this overview omits and pu-erh's own sheng/shou split — lives on [Tea Processing](../concepts/tea-processing.md).

| Type    | Oxidation        | Brew Temp (°C) | Caffeine (per cup) |
|---------|------------------|----------------|--------------------|
| White   | Very little      | 75–85          | ~30–55 mg          |
| Green   | Little           | 70–80          | ~28 mg             |
| Oolong  | Partial          | 85–95          | ~37 mg             |
| Black   | Full             | 95–100         | ~47 mg             |
| Pu-erh  | Fermented / aged | 95–100         | ~40 mg             |

The table summarises the principal contrasts between the five families: their place on the oxidation scale, their recommended brewing temperature (see [Tea Brewing](../concepts/tea-brewing.md)), and the approximate caffeine content of a standard cup (see [Caffeine](../concepts/caffeine.md)).[^s12]

Tea is genuinely good for most people in moderation: it is mostly water, and unsweetened tea is naturally low in calories.[^s16] Added sugar changes that picture, though — the brewed tea itself stays essentially calorie-free, but a heavily sweetened or bottled tea can carry a substantial number of calories, so unsweetened or lightly sweetened brews are the better choice for anyone watching their diet.[^s17]

Tea is best kept away from its four great enemies: light, heat, moisture, and strong odours.[^s13] Most green and black teas are at their best within a year or two of production and should be stored in an opaque, airtight container in a cool, dry place; pu-erh is the notable exception and, like wine, is often deliberately aged for years or decades, with a well-stored cake growing more valued over time.[^s14] Whatever the type, a sealed container away from the spice rack preserves the leaf's aroma far longer than an open tin on a sunny shelf.[^s15]

## See also
- [Camellia Sinensis](camellia-sinensis.md)
- [History of Tea](../concepts/history-of-tea.md)
- [Tea Brewing](../concepts/tea-brewing.md)
- [Tea Antioxidants](../concepts/tea-antioxidants.md)
- [Caffeine](../concepts/caffeine.md)
- [L-Theanine](../concepts/l-theanine.md)
- [Matcha](matcha.md)
- [Tea Processing](../concepts/tea-processing.md)
- [Tea Cultivars](../concepts/tea-cultivars.md)

## Sources
[^s1]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 3-4 — tea's consumption volume, second only to water (ingested 2026-07-16)
[^s2]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 4-6 — strict definition: an infusion from a single plant species (ingested 2026-07-16)
[^s3]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 12-13 — that species named as Camellia sinensis, native range (ingested 2026-07-16)
[^s4]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 13-16 — herbal infusions/tisanes distinguished from true tea (ingested 2026-07-16)
[^s5]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 18-20 — the tea types differ by leaf treatment, not species (ingested 2026-07-16)
[^s6]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 20-24 — oxidation defined as the key processing variable (ingested 2026-07-16)
[^s7]: [raw/tea-guide.md](../../raw/tea-guide.md), line 26 — the families fall along the oxidation spectrum (ingested 2026-07-16)
[^s8]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 28-31 — white and green tea processing (ingested 2026-07-16)
[^s9]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 32-34 — oolong tea's partial oxidation (ingested 2026-07-16)
[^s10]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 35-37 — black tea's full oxidation, aka "red tea" (ingested 2026-07-16)
[^s11]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 38-40 — pu-erh's fermentation and aging (ingested 2026-07-16)
[^s12]: [raw/tea-guide.md](../../raw/tea-guide.md), § Comparison of the Major Types — comparison table of the major tea types (ingested 2026-07-16)
[^s13]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 152-153 — tea's four storage enemies (ingested 2026-07-16)
[^s14]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 153-156 — green/black shelf life vs. pu-erh's aging exception (ingested 2026-07-16)
[^s15]: [raw/tea-guide.md](../../raw/tea-guide.md), lines 156-158 — sealed container storage advice (ingested 2026-07-16)
[^s16]: [raw/tea-health-faq.md](../../raw/tea-health-faq.md), line 9 — tea is genuinely good in moderation, mostly water, low in calories unsweetened (ingested 2026-07-16)
[^s17]: [raw/tea-health-faq.md](../../raw/tea-health-faq.md), line 85 — added sugar in sweetened or bottled tea can carry substantial calories (ingested 2026-07-16)
[^s18]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 48-51 — corroborates: black tea's enzymatic oxidation (hours) vs. dark tea's microbial fermentation (months-years) (ingested 2026-07-16)
[^s19]: [raw/tea-processing-and-cultivars.md](../../raw/tea-processing-and-cultivars.md), lines 38-41 — corroborates: black tea known as "red tea" (hongcha) in China (ingested 2026-07-16)
