 Human language is a system of extraordinary complexity. Nonetheless, young children managed to acquire a first language in a matter of a few years, without a parent effort and without the need of formal instruction. As a starting point, this e-lecture concentrates on the following topics. First, we will look at the relationship between language, language acquisition and cognition. Then we will briefly introduce the main stages of language acquisition and will finally list some fundamental aspects from phonology to semantics, that is, from sound to meaning. First language development has generated much interest in linguistics, psychology and various other disciplines, particularly because it provides concrete answers to various fundamental research questions related to language and cognition. For example, one question concerns the aspect of modularity. Do children acquire language by means of a specialized cognitive device? That is part of their genetic endowment? Or does language emerge from our general cognitive abilities, learned through trial and error skills such as doing addition or riding a bike? We will see. Human uniqueness is another issue. Do only humans possess language or do other species also have the capacity to acquire language? Various attempts to teach chimpanzees and gorillas aspects of human language have not yet produced convincing evidence against the position that language is a uniquely human ability. A further question concerns the relationship between language and thought. Is language simply a tool for expressing our thoughts? Or does the form of language determine the structure of our thought processes? That is, does acquiring a language mean learning to think, not just learning to talk? Well, we will discuss these things in further e-lectures. And finally, the question concerning the relationship between learning and innate-ness. All children have some innate capacity for language, but it depends on where a child is brought up, whether he or she will acquire English or Japanese, for example. So both heredity and environment play a role in language development. But how do the two interact? Well, that's a very important research question in linguistics and psycholinguistics. Let us now look at the central stages of language acquisition. Language acquisition begins very early in the human lifespan. The ascent to adult level competence is a complex process that involves several, more or less distinct stages leading from pre-speech sounds at the very beginning to full sentences at the end or at some sort of end of the acquisition process. It is controversial whether or not discrete phases are involved in the course of language development. The diagram shown here displays the stages that are commonly identified in the relevant literature. Several things are worth noting about these stages. The first question concerns the boundaries between these stages. It is relatively clear that these stages have no clear boundaries. This is indicated by these fading edges. The second question concerns the sequential character of these phases, of these stages of language acquisition. And it is relatively clear that they do not occur in a strict sequence but overlap to some extent. So here we have an overlap, here we have an overlap and here too. While normal children pass through all of these stages, individual stages can be stretched out or can be compressed to a different extent for different children. So in other words, these stages are different in length as far as individual children are concerned here. However, the diagram generalizes over such individual differences. Let us now look at the stages in greater detail. At a very early age, we can identify three stages. Vegetative sounds such as crying, burping or sucking noise. We can find comfort sounds such as cooing and laughing. And we find a stage which is normally labeled by the term vocal play where children produce speech-like sounds where interestingly vowels emerge before consonants. After this period of early vocalization, so this is the period of early vocalization, all young children go through a phase of babbling which lasts for something like six to nine months fading out as the first words appear. By producing these speech-like sounds, infants practice articulatory movements and learn to produce the prosody of their language. There are two types of babbling. Now the first type can be called, so here we have the babbling phase, reduplicated babbling where we find syllables or syllable sequences such as ba-ba-ba that is the repetition of vowel consonant patterns. And we find the system of non-reduplicated babbling, sorry, non-reduplicated babbling where children produce things like ba-da and maybe even gi. First signs of comprehension accompany this stage, so children now learn or acquire the association between situations and strings of sound. And then we can observe a phase which is called one-word utterance phase where children first use names for objects, then they name actions or motions later. They use to pick out thematic roles played by objects such as agent, action and object. And then we find a phase where we can observe an enormous vocabulary burst that is an acceleration in the rate of vocabulary growth. At the same time, these new elements, you might call them words, are combined into more complex constructions and the child gradually uses sentence-like structures. First of all, in terms of two-word utterances where two words are combined expressing various semantic relationships such as agent or action in cases like daddy run. And then again a burst, a morphosyntactic burst where we can discover an enormous increase of inflectional and functional elements. Once children have acquired the ability to produce two and even three-word utterances they start to add function words and grammatical inflections to their utterances. The age of 24 to 30 months has been identified as a period where most children show a kind of flowering of morphosyntax. Towards the age of three we find a stage of telegraphic speech where three or more word combinations with few functional or inflectional elements like milk all gone occur and then even full sentences with increasing utterance length and utterance complexity. Along the way, the child masters the essential ingredients of his language. These central aspects will be discussed in a follow-up e-lecture on language acquisition but let's have a brief look at these central issues first. During the first year of life children achieve control of the speech apparatus and they develop a sensitivity to the phonetic distinctions used in the target language. We will discuss this in a second e-lecture how this is managed. Then we have a level of morphological development that is the acquisition of the relevant morphs plus the rules governing their use in the target language. The children indeed possess morphological rules at a relatively early age has been shown in several classic studies which we will also discuss. And then the big area of syntactic development that is development of sentences starting with one word utterances that do not show any structural properties they are used to name objects in the environment. Later then at the one word stage children also use single words to articulate complex thoughts involving those objects and then more and more complex utterances how they exactly proceed well we will see. Well and finally there's the mental lexicon and the semantic development that deals with word meaning associations. Acquiring a lexicon is a formidable task. It has been estimated that in order to build up an other size lexicon of about 70,000 entries children have to acquire new words at a rate of something like 10 entries per day. How they do manage and how they acquire the meaning of all these items well that's an issue for a follow-up e-lecture. Well as pointed out in this e-lecture there are so many interesting aspects to be said about language acquisition so see you again in Language Acquisition 2.