Improper use of conjunctions, such as "and," "but" and "if," is a significant mistake, even for native speakers. Some foreign languages are either less strict or do not have rules on forming ideas in a single sentence. As a result, English as a second language (ESL) students make this mistake often. A sign of this mistake is when a sentence contains too many of these conjunctions, which usually means there are too many ideas in the sentence.
Improperly pairing plural nouns with singular verbs and vice versa is perhaps the most common mistake ESL students make. Languages such as Mandarin and Spanish either do not have this rule or have an entirely different set of rules regarding singular and plural subjects and verbs. The most common form of this mistake occurs with forms of the verb "to be"--"is," "are" and "am"--paired with the wrong singular or plural noun. Examples of this mistake include "He are eating" and "They is coming."
Non-native speakers tend to compensate for language mistakes by saying or writing wordy sentences. This is a logical mistake to make because the increased number of words provides a higher chance of the listener or reader understanding what the other person is trying to say. However, this tendency can lead to ineffective sentences, confusing or conflicting ideas and run-on sentences.
The typical mistake with adjectives is with using the right form of the adjective to signify level or intensity. Examples of this mistake include "You look more good today," "He looks handsomer than the other guy" and "I am the most fastest runner." This form is particular to the English language, with no clear rules stating when to use the prefix or the suffix forms. This mistake is mostly due to unfamiliarity with vocabulary.