During the first few years of life, children are mastering concrete words (e.g., car, bottle, dog, cat). By age 3, children are likely able to learn these concrete words without the need for a visual reference, so word learning tends to accelerate around this age.[55] Once children reach school-age, they learn abstract words (e.g., love, freedom, success).[56] This broadens the vocabulary available for children to learn, which helps to account for the increase in word learning evident at school age.[57] By age 5, children tend to have an expressive vocabulary of 2,100-2,200 words. By age 6, they have approximately 2,600 words of expressive vocabulary and 20,000-24,000 words of receptive vocabulary.[58] Many claim[who?] that children experience a sudden acceleration in word learning, upwards of 20 words per day,[54] but it tends to be much more gradual than this. From age 6 to 8, the average child in school is learning 6-7 words per day, and from age 8 to 12, approximately 12 words per day.[19]