In linguistics, a word is defined

In linguistics, a word is defined as the minimal free form used in the grammar of a language. Here's a breakdown of what this means:

1. Minimal Free Form:

A word is the smallest unit of language that can stand on its own and act independently. It is not further divided into smaller meaningful units within the grammar of the language being studied.

2. Free Agent: 

A word has a certain level of independence in terms of its position in a sentence. While its position can be influenced by grammatical rules and syntax, it is not completely dictated by other elements in the sentence.

3. Positional Mobility: 

Words can often be moved around within a sentence without affecting the grammaticality or meaning of the sentence significantly. This flexibility in word order contributes to the concept of positional mobility.

4. Stability:

Despite their positional mobility, words themselves are stable units in the sense that their internal structure remains unchanged. The elements within a word (morphemes) do not shift around independently within the word.

Here's an example to illustrate the concept of positional mobility using the sentence variations provided:

• - This old industrialist revisited Lancaster, fortunately.

• - Fortunately, this old industrialist revisited Lancaster.

• - Lancaster, this old industrialist revisited, fortunately.

• - Fortunately, Lancaster was revisited by this old industrialist.

In each of these variations, the words maintain their stability as individual units, but their order within the sentence changes to convey slightly different nuances or emphasis while remaining grammatically correct. This demonstrates how words, as minimal free forms, can exhibit positional mobility in sentence construction.