1. Developing Morphology
1.1. Two-and-a-half year old kids start to discover the grammatical function of the nouns and verbs.
1.1.1. The first Inflectional Morpheme to appear is the -Ing form. E.g: "Mommy smiling".
1.1.1.1. The next one is the -S plural form. E. g: "Dogs". However, kids overgeneralize this rule saying "Mans"
1.1.1.1.1. Following the previous ones, kids start to use Irregular Past-Tense and some forms of verb To Be. Afer this, the -Ed Inflection appears, however in some cases the Past-Tense is replaced with the -Ed form creating words such as "Goed".
1.1.1.1.2. Finally, the regular -S on Third person singular present tense appears, at the beginning with full verbs for example "Comes" and then with auxiliaries "Does" and "Has".
1.1.1.2. On the other hand, once they start using - ed as in "houses" they will say words such as "Footses".
1.1.1.3. At the same time, some kids begin to use "Irregular plural" such as "men", despite this they start to combine the it with the -S form saying "Some mens". Later on, they star to use the Possessive Inflection -'S as in "Moomy's book".
2. Developing Syntax
2.1. In the formation of questions and the use of negatives there appear to be 3 stages: Stage 1 (18 - 26 months), Stage 2 (22-30 months), and Stage 3 (24-40 months).
2.1.1. - Forming questions.
2.1.1.1. The first Stage has two procedures, th first one is when Wh- form (Where, Who) is added at the beginning of the expression. E. g: "Where Kitty?". The secind one is the rise of the intonation at the end of the sentences. E. g: "Doggie?".
2.1.1.1.1. - Forming negatives.
2.1.1.2. The second stage is when children begin to use more complex expression with the same intonation as in the first stage, moreover they use other Wh- forms (What, Why). E. g: "Why you smiling?".
2.1.1.3. In the third stage, questions are quite better than the second stage, however some issues with the structure of Wh- questions and the morphology of verbs are noticeable. E. g: "Did I caught it?". At the same time kids start to use the auxiliary in English questions "Can I have..".