flag
flag — noun
1. a square or oblong sheet of fabric marked with a distinctive design, used as the
a square or oblong sheet of fabric marked with a distinctive design, used as the official emblem of a country, a group of people, or an organization.
Tariro hung a Japanese flag outside her window during the World Cup.
flag + of [country]
The stadium was covered with flags from more than two hundred nations.
Soldiers stood at attention while the national flag was raised at dawn.
Every ship in the harbour flew a bright red signal flag for the holiday.
The Olympic flag has five coloured rings on a white background.
文法句型
flag + of + country/organization
用法筆記
National flags are often paired with verbs like raise, lower, fly, wave, and fold. Countries also use their flag as a symbol in contexts such as war, diplomacy, and sport.
常見錯誤
2. in American football, a small yellow cloth square that the referee throws onto t
in American football, a small yellow cloth square that the referee throws onto the field to show that a player has broken a rule.
The referee threw a yellow flag when the defender grabbed the receiver's arm.
throw a flag for [violation]
Shanti knew her team would lose yardage when she saw the flag on the grass.
A flag for holding pushes a team back ten yards from the foul spot.
The home crowd booed when a flag halted their team's best play.
文法句型
throw a flag
flag for + [violation type]
用法筆記
In American football, the yellow penalty flag is a physical cloth. The verb sense (verb/5) describes the official's action of throwing it.
3. something that shows a possible problem, danger, or cause for concern, especiall
something that shows a possible problem, danger, or cause for concern, especially before the problem becomes serious.
A sudden drop in sales was a red flag for the company's management team.
red flag — metaphor for a serious warning
Brooke noticed several warning flags in the contract before she signed it.
Teachers learn to spot flags that may show a child is struggling at home.
The lack of receipts raised a red flag during the tax audit last spring.
- warning sign
more general; less metaphorical than red flag
- indicator
neutral term; can be positive or negative
- alarm bell
stronger; suggests an immediate danger
文法句型
red flag
flag for + [concern]
用法筆記
Red flag is the most common form. It is often used in business, healthcare, and security contexts to describe early indicators of risk.
常見錯誤
4. a flat piece of stone, usually square or rectangular, used to cover floors, path
a flat piece of stone, usually square or rectangular, used to cover floors, paths, patios, or other outdoor surfaces.
The garden path was made of grey flags that had been there for decades.
Dario laid new sandstone flags across the patio behind his house last weekend.
lay + flags — construction collocation
Moss had grown between the old flags in the courtyard of the cathedral.
The kitchen floor was covered with large uneven flags of local stone.
- flagstone
the full form; more formal and technical
- paving stone
general term for any stone used in paving
- slab
larger and thicker; used for concrete or stone surfaces
文法句型
flagstone
flag + [stone type]
用法筆記
Often shortened from flagstone. The plural flags is very common when describing paved areas. Not to be confused with the cloth senses.
5. a waterside plant belonging to the iris family, with long sword-shaped leaves an
a waterside plant belonging to the iris family, with long sword-shaped leaves and showy flowers that are usually yellow, blue, or purple.
Yellow flags grew wild along the edge of the stream behind the old mill.
flag + colour + location (plant sense)
Eleni planted blue flags near the pond in her grandmother's cottage garden.
The long green leaves of the flag rose from the damp soil like swords.
In early summer, purple flags bloom across the marshy area of the nature reserve.
- iris
the broader botanical category that includes flags
- sweet flag
a related waterside plant (Acorus calamus), not a true iris
用法筆記
This sense is uncommon in everyday conversation. It mainly appears in gardening and nature writing. Yellow flag (Iris pseudacorus) is the most common type mentioned.
flag — verb
1. to put a physical or digital mark on something so that it can be found or identi
to put a physical or digital mark on something so that it can be found or identified more easily later among other things.
Hao flagged the important pages in the report with small yellow sticky notes.
flag + noun + with [tool]
The librarian flagged every book that had not been returned by the due date.
Roya flagged the emails from her manager so she could read them first.
Brandon flagged the sections of the proposal that still needed revision before the board meeting.
Each item on the list was flagged as urgent or routine by the assistant.
文法句型
flag + noun phrase + for + purpose
flag + noun phrase + as + category
用法筆記
This sense is about personal organisation — you flag something to help yourself find it later. Distinguish from verb/3, where you flag something to warn others about a problem.
常見錯誤
2. to mark computer data or an item in a system with a true/false value so that it
to mark computer data or an item in a system with a true/false value so that it can be identified, filtered, or processed in a specific way by the program.
The security system flags any file that contains suspicious code for the team to inspect.
flag + noun + for + [action]
Hyun wrote a script that flags user accounts that have been inactive for six months.
The payment system flags transactions over ten thousand dollars for manual review.
Each database record is flagged as active or archived by the program.
- tag
can add any type of metadata, not just boolean values
- label
more general; used in both programming and everyday language
- set a flag on
more technical; describes the actual programming operation
文法句型
flag + noun + as + boolean value
flag + noun + for + processing
用法筆記
Closely related to verb/1 in the action of marking, but this sense specifically involves a binary (true/false) or categorical value in a computing context. Frequently passive: items are flagged by the system, not by a person.
3. to tell someone about something important or problematic so that they can take a
to tell someone about something important or problematic so that they can take action, especially before it becomes a bigger issue.
The school nurse flagged the student's allergy to the new teacher before the class trip.
flag + noun + to + recipient
A neighbour flagged the broken streetlight to the city council after the accident.
The audit report flagged several financial problems that needed immediate attention.
Gita flagged that the shipping address was wrong before the package went out.
Users can flag offensive comments on the website for moderators to review.
文法句型
flag + noun + to + person
flag + noun + for + reason
flag + that-clause
用法筆記
Distinguish from verb/1: flagging a problem (verb/3) means drawing others' attention so they can act; flagging a page (verb/1) is for your own future reference. British English also uses flag up (phrasal verb) for this sense.
常見錯誤
4. to become physically tired, lose strength or energy, or start to decline in qual
to become physically tired, lose strength or energy, or start to decline in quality, interest, or effectiveness over time.
Eli's energy began to flag after walking for eight hours under the hot desert sun.
Nora's interest in the project flagged when she saw how much paperwork was involved.
subject [interest/enthusiasm/energy] + flag — typical subject pattern
The conversation flagged after everyone ran out of new things to talk about.
Public support for the new law flagged as more people learned about the cost.
- strengthen
the opposite direction of change
- pick up
informal; to recover lost energy or pace
文法句型
flag + adverb of degree
flag + under + pressure
用法筆記
Intransitive only — you never flag something in this sense. The subject is typically energy, enthusiasm, interest, conversation, spirits, or support. Describes a gradual process, not a sudden stop.
常見錯誤
5. (in sports, especially American football) for an official to raise or throw a fl
(in sports, especially American football) for an official to raise or throw a flag to signal that a player has broken a rule, or to penalize a player for doing so.
The referee flagged the defender for holding the receiver's jersey during the play.
flag + player + for + [violation]
The official flagged the runner for starting before the starting gun sounded.
Élise was flagged for a dangerous tackle during the championship semifinal match.
The linesman flagged as soon as the forward passed the last defender.
- penalize
broader; applies to any sport and can mean giving a penalty without using a flag
- call a penalty on
describes the refereeing decision, not specifically the flag gesture
文法句型
flag + player
flag + player + for + violation
flag (no object)
用法筆記
Can be transitive (the official flags the player) or intransitive (the official simply flags, without naming who). In American football, throwing a yellow flag is the physical act; flagging is the official's decision to do so.