The main difference is that a lexical chain is beneficial, whereas a tautology can be detrimental to, or have no effect on your writing at best. Let's take a look at what each of those concepts entails:
Lexical chain:
A lexical chain is a sequence of semantically related lexical terms, independent of the grammar structure of the text. Consider the following example:
As you can see, the writer varies the terms used throughout this paragraph, although they are essentially referring to the same thing, yet using different terms. Consider the terms highlighted in green (
"Macbeth",
"the play",
"this text",
"piece of theatre"). While the author is referring to the same thing (i.e. Macbeth), they are doing so using a variety of terms, which gives their paragraph sophisticatedness, instead of using terms like "Macbeth" every time you wish to refer to this play.
The same concept applies to the terms highlighted in yellow and those highlighted in pink.
Tautology:
A tautology is a needless repetition of a single concept. It is considered to be a fault relating to writing style. Examples of sentences/expressions where tautology applies include:
- "An armed gunman"
- "She always over exaggerates"
If you observe the above examples closely, you may notice that you may omit certain words that add no meaning/useful information to the sentence. In the first sentence, we can omit
"armed" as one would normally assume that a gunman is armed, meaning that there is no need to include that word in that sentence.
In the case of the second sentence, we can omit the word
"over" as one already knows that exaggeration is excessive, meaning that the word
"over" does not add much meaning/useful information to the sentence.
Tautology may occur in essay writing, particularly if a student wishes to increase their word count. For example, writing
"depreciates in value" instead of simply writing
"depreciates" may constitute tautology.
I hope this helps!