Child development researchers have revealed the 25 words that children should be able to say by the time they turn two.

However, other experts have called into question whether a child’s development is so prescriptive, and have reassured parents that their child is not abnormal if they do not know these exact terms.

Researchers at the US Child Study Institute at Bryn Mawr College identified the minimum 25 “must know” words for toddlers, including: "mummy", "daddy", "baby", "milk", "juice", "hello", and "bye".

If a child does not know the words listed it could be a sign that they have developmental problems, hearing problems, or autism, the New York Daily News reported.

The study, which was published in 2012, has recently re-emerged after it was reported by The Sun.

As many as 1 in 10 children in the UK have a problem with language and communication, according to the communication charity Talking Point.

Responding to the study, Dr Kirsten Abbot-Smith, Lecturer in Developmental Psychology and Co-director of Kent Child Development Unit, said that if a child cannot say 25 recognisable words by 2, parents should refer them to a speech and language therapist for assessment.

But she also stressed that the specific words will depend on what the child hears in its environment, as well as its needs and interests.

The 25 words researchers say children must know Mummy

Daddy

baby

milk

juice

hello

bye-bye

yes

no

dog

cat

ball

nose

eye

banana

cookie

car

hot

thank-you

bath

shoe

hat

book

more

all gone

A child’s ability to understand is more important in the long-term than their ability to speak, she added.

"If a 2-year-olds has significantly greater difficulties understanding what others are saying to him or her when the child cannot rely on contextual cues and or cues such as pointing and eye-gaze direction, then this can indicate neuro-developmental difficulties of one type or another," she said.

However, studies show that parents find it difficult to identify whether their child has a problem with language comprehension. Dr Abbot-Smith advised those who are concerned to fill out an online questionnaire, such as that offered by Talking Point, which can help to decide whether a child needs.

Elena Lieven and Caroline Rowland, co-directors at ESRC International Centre for Language and Communicative Development, mirrored Dr Abbot-Smith's response, and said that children show "large individual differences" as they develop their skills.

They explained that if a child is enthusiastic about a certain topic, for example trains, they will know more words about relating to that.

"25 words by 2 isn't very many, but it is more important, perhaps, if your child isn't understanding and responding to quite a lot words by 2, because half of late talkers catch up," they said via email.

"What a children's earliest words are also depends on the age at which they start talking - a late talker who is already mobile will learn words for the toys and objects that they find around them, while early talkers may learn more conversational words, for example hello, bye bye, or thank you."

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Parents can help their children to develop their language by improving the quantity and quality of their verbal interactions, said Dr Abott-Smith.

"By quality, what appears to be important is contingency, that is talking about your child’s focus of attention and responding to your child’s verbal and non-verbal initiations by providing responses that are temporarily contingent and related in terms of conversation topic."