Semantics is the line of study concerned with deriving meaning from utterances. This involves several concepts including sentence relations to which presupposition and entailment belong. This category involves other concepts such as; synonymy, contradiction and tautology. This paper serves to establish the understanding of sentence relations, paying particular attention to presupposition and entailment, and the differences between these concepts to the effect of clarifying the confusion existent in there between.

Words do exhibit relations with one another in a language, sentences also do exhibit relations to one another. This means that sentences also relate in a specific way. You will find that words have relation that cause them to have similar meaning, also with sentences, they have specific relations of which such relations may be led by the reason of the use of particular words. Sometimes these relations may be of certain syntactic structure. But for one to know or be familiar with sentence relations, he or she must understand different concepts that fall under sentence relations. These are; synonymy, tautology, contradiction, entailment and presupposition. Below will be the description of each concept, basing more focus on entailment and presupposition.
Huang defines presupposition as ‘a proposition or an inference whose validity is taken for granted for a sentence to be true or for a speech act to be felicitous’, (Huang, 2007). Presupposition constitute at any given time the communicative background assumed to be known and accepted (Franck 1973). In most cases, people use presuppositions throughout without knowing it. For one to understand presupposition, first they must know the definition of what presupposition is, the types of presuppositions, what they do and how one can identify them. Also, one must be able to know what causes presuppositions, which is referred to as presupposition triggers.
Kroeger defines presupposition as ‘information that which is linguistically encoded as being part of the common ground at the time of utterance’, (Kroeger 2018). With common ground, Kroeger refers to everything that both the speaker and the hearer know or believe, also know that they have in common. This means that during the time of utterance, the hearer has the knowledge of what is being said by the speaker. Examples that are obvious include; knowledge about the world, we all know that there is one moon and one sun. This is a fact that no one can dispute or argue because evidence is already there. This may also continue to include knowledge that is observable in speech situations, the perfect scenario will be what the speaker is wearing or carrying. Also facts that have been mentioned before in that same conversation or discourse. From the above, we can simply say, a sentence is said to presuppose another sentence if its truth and that of its negation both imply that the presupposed sentence is also true.
It is surprising that Magang passed the test.

Presupposition: Magang passed the test.

It is not surprising that Magang passed the test.

Presupposition: Magang passed the test.

The table below shows how presupposition relate or the structure in which it follows.

T or F?T
P presupposes q if q is part of the assumed background against which P is said. This simply means that q hold the same idea as P.

In pragmatics, entailment can be defined as the relationship that is found between two sentences, where the truth of one sentence requires the truth on another sentence. The truth of sentence B requires the truth of sentence A. this means that entailment can be referred to as a relationship that is found between two propositions that are expressed by two sentences.

Matome is an intelligent student.

Ent: Matome is a student.

Raymond and Lorato flunked.

Ent: Lorato flunked.

Lorato and Raymond flunked.

Ent: Someone flunked.

Mary broke the window.

Ent: The window broke
Tumelo and Ditiro went to the party.

Ent: Ditiro went to the party.

Ent: Tumelo went to the party.

Thabo is a bachelor.

Ent: Thabo is married.

F<T or F
T or F?T
From the above sentences, one can note that there are sentences that are entailed on the other sentences. The “Thabo is a bachelor” entails “he is a bachelor” when the pronoun ‘he” refers to ‘Thabo’. To the hearer, this will make sense because they already know that a bachelor the speaker is referring to is Thabo.

Presupposition and entailment differ. When a presupposing sentence is negated, the presupposition survives as in examples 19 and 20:
19.I regret studying law
Pres: I studied law
20.I do not regret studying law
Pres:I studied law

However, in entailment, negating the entailing sentence results in the failure of the entailment as in the following examples:
21.Peter is my brother (
22. I have a brother (entailment holds)
23.Peter is not my brother
24.I have a brother (we are not sure whether I have a brother or not hence entailment no longer holds)