rad
Abbreviation with 5 meanings
| Stands for | Radian |
|---|---|
| Meanings | 5 |
| Categories | Units & Measurements, Medical |
| Also written | RAD |
rad has five meanings. The most common are Radian (metric and SI unit) and Reactive airway disease (respiratory); it can also stand for Reactive attachment disorder, Right axis deviation and Rad (radiation absorbed dose).
Meanings of rad at a glance
| # | rad stands for | Context |
|---|---|---|
| 1 | Radian | Units & Measurements › Metric and SI Unit |
| 2 | Reactive airway disease | Medical › Respiratory |
| 3 | Reactive attachment disorder | Medical › Mental Health & Psychiatry |
| 4 | Right axis deviation | Medical › Cardiology |
| 5 | Rad (radiation absorbed dose) | Units & Measurements › Engineering Unit |
1. Radian
Units & Measurements · Metric and SI Unit Abbreviations
The SI unit of plane angle: the angle at the center of a circle subtended by an arc equal in length to the radius. A full circle is 2π rad, about 6.283, so one radian is about 57.3 degrees.
Example: Switch the calculator to rad mode before evaluating sin(pi/6).
Radians are the default in calculus, physics and programming languages because the derivative of sin x equals cos x only when x is in radians. Wrong answers in trigonometry homework often come from a calculator left in DEG instead of RAD mode. The term appeared in print in 1873 in examination questions set by James Thomson. Rad is also an obsolete radiation-dose unit.
2. Reactive airway disease (RAD)
Medical · Respiratory Abbreviations
Loose clinical label for episodes of wheezing, cough and bronchospasm, often used for young children before a firm asthma diagnosis can be made or for adults with asthma-like symptoms after infections. It is not a specific diagnosis.
Example: Two-year-old with third wheezing episode this winter; RAD, albuterol via spacer as needed.
Many pulmonologists discourage the term because it can delay a proper asthma diagnosis and treatment or lump together unrelated conditions. Reactive airways dysfunction syndrome (RADS), by contrast, is a specific irritant-induced asthma after a single high-level exposure, described in 1985 and seen in some September 11 responders. In cardiology RAD means right axis deviation.
3. Reactive attachment disorder (RAD)
Medical · Mental Health & Psychiatry Abbreviations
Rare disorder of young children who experienced severe neglect or frequent changes of caregiver, in which the child rarely seeks or responds to comfort and shows limited positive emotion. Diagnosis requires a developmental age of at least nine months, with onset before age five.
Example: RAD after institutional care until age 3; withdrawn, rarely seeks comfort; dyadic caregiver therapy.
DSM-5 split the older RAD diagnosis into this inhibited form and disinhibited social engagement disorder, in which children are overly familiar with strangers. Stable, responsive caregiving is the main treatment. RAD is often overdiagnosed in adopted children with other conditions. In cardiology RAD means right axis deviation, and in respiratory medicine reactive airway disease.
4. Right axis deviation (RAD)
Medical · Cardiology Abbreviations
ECG finding in which the QRS axis lies between +90 and 180 degrees, shown by a negative QRS in lead I and a positive QRS in aVF. It suggests right ventricular hypertrophy, pulmonary embolism, chronic lung disease, left posterior fascicular block or lateral myocardial infarction.
Example: New RAD and sinus tachycardia in a postoperative patient: evaluate for pulmonary embolism.
Right axis deviation is normal in infants and young children, whose right ventricle remains relatively dominant, and can be seen in tall, thin adults. Swapped left and right arm leads produce a false right axis with an inverted P wave in lead I. In respiratory medicine RAD means reactive airway disease.
5. Rad (radiation absorbed dose)
Units & Measurements · Engineering Unit Abbreviations
An older unit of absorbed radiation dose equal to 0.01 gray, or 100 ergs per gram. It survives mainly in older American texts and in radiation oncology, where the centigray is treated as its equivalent.
Example: The 1960s report lists tumor doses in rad, so multiply by 0.01 to get gray.
Introduced in 1953 and replaced by the SI gray in 1975; one rad equals one cGy. The lowercase symbol rad is far more often the radian, the SI unit of angle, so check the context of any document that uses it.
Related abbreviations
More metric and SI unit abbreviations
- P – Peta- (quadrillion)
- pc – Parsec
- q – Quecto- (10^-30)
- R – Ronna- (10^27)
- S – Siemens
- SI – International System of Units
- sr – Steradian
- Sv – Sievert
See all 64 metric and SI unit abbreviations →
More respiratory abbreviations
- PRVC – Pressure-regulated volume control
- PSG – Polysomnography
- PSV – Pressure support ventilation
- PTX – Pneumothorax
- RDI – Respiratory disturbance index
- RDS – Respiratory distress syndrome
- RLL – Right lower lobe
- RML – Right middle lobe
See all 109 respiratory abbreviations →
This entry is for general education and is not medical advice. Abbreviation use varies between institutions; always confirm in context.