英语单词的本义及词义扩展规则

下面以英语单词cast为例来说明英语单词的本义及词义扩展规则，这些规则性足以支撑我们快速理解记忆单词词义，为我们学习英语单词提供高效的方法。 

Core Meaning (Etymology & Literal Sense) 

The fundamental and oldest meaning of the verb cast is to throw something with force, often with a deliberate aim or motion. This originates from Old Norse kasta (to throw). 

Examples: 

• "The knight cast the sword into the lake." (Literary/archaic)

 • "He cast his fishing line into the river." 

Extended Meanings & Rules of Semantic Extension

 The vast network of meanings for "cast" derives almost entirely from metaphor. The core idea of "propelling something outward from a source" is applied to non-physical domains. The extension follows several clear patterns:

 Rule 1: From Physical Throwing to Non-Physical Projection

 This is the most productive rule. The act of throwing is metaphorically extended to sending forth something intangible in a specific direction.

 • Projecting Looks/Expressions:cast a look/glance/smile (To direct one's gaze or expression as if throwing it).

 • Projecting Light/Shadow:cast light/shadow (For a light source to send forth rays or create a shadow upon a surface).

 • Projecting Influence/Atmosphere:cast doubt/a shadow/aspersions on (To cause an abstract quality like doubt, gloom, or criticism to fall upon a person or situation).

 • Projecting Magic/Thought:cast a spell (To send forth magical influence); cast your mind back(To send your thoughts back to an earlier time).

 Rule 2: From Throwing (a Net or Die) to Selecting and Assigning

 This meaning comes from the older practice of "casting" lots (throwing dice or marked stones) to make a decision or a prediction.

 • Selecting Actors:to cast an actor in a role (To select and assign a role to a performer, as if deciding by lot or choice). The noun the cast refers to the entire group of selected actors.

 Rule 3: From Throwing/Pouring (Liquid) to Shaping by Molding

 This involves the specific action of throwing or pouring a fluid substance into a mold where it hardens.

 • Creating an Object:to cast a statue in bronze (To form by pouring molten metal into a mold).

 • Medical Immobilization:a plaster cast (A rigid bandage molded to protect a broken limb, named for its similar forming process).

 Rule 4: From Making a Forceful Throwing Motion to Making a Formal Action

 The formal, deliberate nature of a throw is applied to other decisive, formal acts.

 • Voting:to cast a/your vote (To formally record one's choice in an election).

 Rule 5: From Throwing Off (an Outer Layer) to Shedding

 This is a more specialized, literal extension of the "throw off" sense.

 • Animals Shedding Skin:A snake casts its skin. (To shed and leave behind its old outer layer).

 Summary 

The semantic expansion of cast is a classic example of metaphorical extension. Starting from the concrete action "to throw," it developed meanings by applying the concept to: 

1. Directed Emission: Of light, looks, influence, and thoughts.

 2. Formal Selection/Decision: In entertainment (actors) and civics (votes).

 3. Shaping via Molding: In manufacturing and medicine. 

4. Discarding: In zoology (shedding skin). 

This process creates a coherent word family where the sense of "directed outward projection from a source" links all its modern uses.