Modulation is made up of obligation and inclination。 Halliday (2008: 147) points out in his book that in a command, the intermediate points represent degree of obligation such as must, should, need, have to, allowed, supposed, required, etc。 while in an offer, they represent degree of inclination such as will, must, can, willing, keen, determined。

Modality system can be illustrated as follows (Thompson, 2000: 58):

Modality Modalization Probability: She is certainly right。

Usuality: He often helps others。

Modulation Obligation: You should hand in your phones。

Inclination: I will give you a hand。

Table 3。1 Types of modality

According to Halliday (2008), interpersonal meanings of modality system are often realized by modal expressions or adjuncts。 Every modal expression or adjunct has its own value。 Value is the intensity of modal factors which express modalization and modulation。 In terms of modalization, value means the degree of certainty。 With modulation, value is concerned with the degree of determination to a proposal。 According to Halliday (2000: 358), modality has three levels: high, median and low value。 The three values of modality can be shown in table 3。2。 

Probability Usuality Obligation Inclination 来.自^优+尔-论,文:网www.youerw.com +QQ752018766-

High definitely always must/required will

Median probably frequently should/supposed keen

Low may seldom need willing

Table 3。2 Three values of modality

3。3 Person System

    In addition to the mood system and the modality system, person system is also a main way to realize interpersonal meanings in English commercials。 Halliday (2000) points out that in grammar, the first person refers to the speaker himself, the second person is the speaker's reference to addressee or receiver and the third person refers to other people who are not present in the discourse。 In English commercials, advertisers always use the person system to create an intimate atmosphere, to shorten the social and psychological distance to the readers。 Then this system makes the products or services more easily accepted by the customer。

The first personal pronouns, such as I, we and their corresponding forms, me, my, mine, us, our and ours are necessary factors to the combination of products or service and their company。