"I have a dream" is a speech addressed by Martin Luther King on 8th August, 1963 in front of Lincoln Memorial Hall in memory of 100 anniversary of "Black Emancipation Declaration". It mainly exposes the brutal persecution on blacks, expresses the desire for freedom and determination for happiness and justice. The speech has also influenced the whole generation of young people at that time.

The speech advocates that we should not judge someone on the color, status, family but on their content of characters. Everyone is born equal, there is no distinction between highborn and lowborn.

The use of language in the speech presents the rules and characteristics affected by register factors, such as language field, mode and tenor of discourse. In the entire speech, there are no very uncommon words or phrases and no special long terms, most of which are basically common in daily life, people often hear about the vocabulary. Martin Luther King's audience are mostly black with different cultural and educational background. first of all, it is to make all the audience understand his speech.

The theme of the speech is about for black rights and obtain real freedom. Thus, Martin Luther King's lecture revolves around this theme and uses a number of parallel sentences. The high-frequency vocabulary that appears in the discourse must be clearly related to the subject. I have done a simple counting, "freedom" appeared 20 times in the speech, "justice" 11 times, "right" 7 times. From this point of view, The speech is closely related to the theme and highlight its purposes, on the other hand, it expressed strong desire to achieve his goal and strong appeal to the audience.