The apprehensive anticipation of future danger
or misfortune accompanied by a feeling of worry, distress, and/or somatic symptoms of tension. The focus of anticipated danger may be
internal or external.

Characteristics of Anxiety

• Feeling apprehensive
• Feeling powerless
• Having sense of impending danger, panic or doom
• Having increased heart rate
• Breathing rapidly
• Sweating
• Trembling
• Feeling weak or tired   
  (Source: Mayo Clinic)

Phobia:

Persistent fear, anxiety, and avoidance of a specific object or
situation that is out of proportion to the actual danger that the object
or situation poses.

(Source: DSM-5)

Panic Disorder:

Panic disorder refers to recurrent unexpected panic attacks. A panic
attack is an abrupt surge of intense fear or intense discomfort that
reaches a peak within minutes. Followed by concern about additional
attacks, and a maladaptive change in behavior related to the attacks.

Characteristics of Panic Disorder

•  Heart palpitations
• Sweating
• Trembling or shaking
• Sensations of shortness of breath or smothering
• Feelings of choking
• Chest pain or discomfort
•  Nausea
•  Feeling dizzy/light-headed
• Chills or heat sensations
• Numbness or tingling sensations
• Derealization (feelings of unreality)
• Depersonalization (being detached from oneself)
• Fear of losing control
• Fear of dying
  (Source: DSM-5)

Generalized Anxiety Disorder:

Excessive anxiety about a number of events or activities occurring more
days than not for at least 6 months, and causes significant distress or
impairment in functioning.

Characteristics of Anxiety Disorder

• Difficulty controlling the worry
• Restlessness or feeling keyed up or on edge
• Being easily fatigued
• Difficulty concentrating or mind going blank
• Irritability
• Muscle tension
• Sleep disturbance
  (Source: DSM-5)