# fluid

/ˈfɫuəd/ (US) · /flˈuːɪd/ (UK)

Source: https://englishreference.com/word/fluid
Updated: 2026-06-19

## Senses

### 1. liquid or gas

noun · CEFR B2 · Technical

any substance that flows easily and takes the shape of its container, such as water or air.

For teachers: a substance, such as a liquid, gas, or plasma, that deforms under shear stress and conforms to the shape of its container.

- The mechanic checked the levels of the brake fluid in the car.
- The laboratory equipment was designed to measure the viscosity of various industrial fluids under extreme pressure conditions.

### 2. medical liquids

noun · CEFR C1 · Technical

liquids given to a patient, often through a tube in the arm.

For teachers: intravenous solutions administered to a patient to maintain hydration or deliver medication.

- The doctor said the patient needed more fluids to recover from the fever.
- The nursing staff monitored the administration of intravenous fluids to ensure the patient remained stable after the surgery.

### 3. changing easily

adjective · CEFR B2

likely to change; not fixed or settled.

For teachers: subject to change or transition; characterized by a lack of fixed structure.

- The travel plans are still fluid because we haven't booked the flights yet.
- The political situation remained fluid as negotiators struggled to reach a consensus before the midnight deadline.

### 4. smooth motion

adjective · CEFR B2

moving in a smooth and beautiful way.

For teachers: characterized by a smooth, elegant, and continuous quality of motion.

- The dancer's movements were fluid and graceful.
- The athlete's fluid running style allowed him to maintain a high pace without appearing to exert significant effort.

### 5. available cash

adjective · CEFR C1 · Formal · Technical

describes money or assets that can be used or moved easily.

For teachers: referring to assets that are easily converted into cash without significant loss of value.

- The company needs to keep some fluid assets to pay for unexpected repairs.
- The investment firm advised the client to maintain a portion of their portfolio in fluid capital to respond to market volatility.

## Examples

- The doctor told me to drink plenty of fluids.
- Mechanics checked the car for leaks to ensure all hydraulic fluids were at the correct levels for safe braking.
- The patient's recovery was aided by the careful administration of intravenous fluids to maintain electrolyte balance and prevent dehydration during the acute phase of the illness.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.