A–Z Vocabulary
High-value IELTS words starting with O — obsolete, optimal, overarching and more — with definitions, examples and memory tricks.
10 / 10 words
adjective
Definition
No longer produced or used; out of date.
Example sentence
“Many traditional retail jobs may become obsolete as automated checkout systems expand.”
Memory trick
Sounds like 'old sleet' — old, melted away, no longer useful.
Common collocations
verb
Definition
To block or get in the way of something.
Example sentence
“Vested interests have repeatedly obstructed meaningful reform of the tax system.”
Memory trick
'Ob-' (against) + 'struct' (build) — building something to block the way.
Common collocations
adjective
Definition
Best or most favourable; ideal.
Example sentence
“Determining the optimal balance between privacy and security remains a key policy challenge.”
Memory trick
From 'optimum' — the best possible point.
Common collocations
adjective
Definition
Comprehensive; covering or affecting everything.
Example sentence
“The overarching aim of sustainable development is to balance social, economic, and environmental needs.”
Memory trick
Like a giant arch over everything — overarching covers all.
Common collocations
adverb
Definition
Apparently or purportedly, but perhaps not actually.
Example sentence
“The policy was ostensibly designed to reduce emissions, though critics argue it primarily benefits incumbents.”
Memory trick
From 'ostentation' — outwardly showing, but possibly not real.
Common collocations
noun
Definition
The way a thing turns out; a consequence.
Example sentence
“Educational outcomes are strongly correlated with the socioeconomic status of students' families.”
Memory trick
What 'comes out' of an event — the outcome.
Common collocations
noun
Definition
The start or beginning of something.
Example sentence
“From the outset, the project was hindered by unclear governance and inadequate funding.”
Memory trick
Like 'out-set' — when you 'set out' on a journey, that's the outset.
Common collocations
noun / verb
Definition
A thorough examination and reorganisation with the aim of improvement.
Example sentence
“The country's public transport system is in urgent need of a comprehensive overhaul.”
Memory trick
Like hauling a ship out for repair — a complete inspection and fix.
Common collocations
verb
Definition
To make the best or most effective use of a situation or resource.
Example sentence
“Companies are using AI to optimise supply chains and reduce environmental impact.”
Memory trick
From 'optimum' — making something achieve its best.
Common collocations
verb
Definition
To dominate or appear more prominent than; to cast a gloom over.
Example sentence
“Short-term economic concerns continue to overshadow longer-term environmental priorities.”
Memory trick
Casting a shadow over something — making it less visible.
Common collocations