delta
/ˈdeltə/ (bre, ipa) · [dˈɛltə] /ˈdeltə/ (ame, ipa) · [dˈɛltə] /ˈdel-tə/ (ame, mw)
delta — noun
- deltasingular
- deltasplural
1. a wide, fan-shaped tract of land at a river's mouth, formed as the main stream s
a wide, fan-shaped tract of land at a river's mouth, formed as the main stream splits into separate channels that empty into the ocean or a large lake.
The Nile Delta is known for its rich soil and large farming communities.
proper noun: the Nile Delta as a named region
Ishaan studied the map and saw the river formed a wide delta at the coast.
Many birds spend the winter in the wetlands of the Mississippi Delta.
The Mekong Delta is one of the most important farming areas in Southeast Asia.
Farmers near the delta rely on yearly floods to bring fresh soil to their fields.
- estuary
an estuary is where a river meets the sea with a single, wide channel affected by tides; a delta has multiple branching channels.
- floodplain
a flat area beside a river that floods; a delta is specifically at the river mouth where it splits.
用法筆記
Often capitalised as part of a place name, e.g. the Nile Delta, the Mekong Delta.
常見錯誤
2. Delta (Δ, δ) is the character that occupies the fourth position in the Greek wri
Delta (Δ, δ) is the character that occupies the fourth position in the Greek writing system, and is widely used as a symbol in mathematics and science.
In maths class, the teacher used delta to show a change in a number.
usage in mathematics to represent change
Nadia wrote a small delta symbol next to the equation.
The Greek alphabet starts with alpha, then beta, gamma, and delta.
Scientists often use the delta sign to mean 'a difference' or 'a change' in numbers.
Chiara could not remember whether delta comes before or after gamma in the alphabet.
用法筆記
In science and mathematics, the uppercase Δ is commonly used as a symbol meaning 'change in' (e.g. Δt = change in time). The lowercase δ often means a small amount.
常見錯誤
3. a fast-spreading strain of the coronavirus that causes COVID-19, given the name
a fast-spreading strain of the coronavirus that causes COVID-19, given the name Delta by global health authorities in 2021, which quickly became the most common source of new infections around the world.
Many countries closed their borders again when the Delta variant began to spread quickly.
historical context: travel restrictions during Delta wave
Hao got vaccinated at the end of 2021 to protect himself against the Delta variant.
Health officials said the Delta variant spread more easily than earlier forms.
Schools asked students to wear masks again after Delta variant cases appeared.
用法筆記
Usually capitalised (Delta variant) as a proper name assigned by the WHO naming system for variants of concern. Now mostly of historical reference since the Omicron variant replaced it.
常見錯誤
4. any object or shape that looks like a triangle, named after the triangular form
any object or shape that looks like a triangle, named after the triangular form of the capital Greek letter delta (Δ).
The Concorde aircraft had a distinctive delta wing that swept back in a wide triangle.
compound: delta wing for a triangular aircraft wing shape
Talia pointed at the delta-shaped road sign that warned drivers about the sharp bend ahead.
collocation: delta-shaped road sign
A delta-shaped logo stood above the entrance to the Greek restaurant on Main Street.
The ancient symbol looked like a delta with three dots above it.
- triangle
triangle is the general geometric term; delta is used when the shape specifically resembles the Greek letter Δ.