The 'face with tears of joy' emoji - 'emoji' was declared the 'word of the year 2015' by Oxford Dictionaries - was the most popular emoji used on Twitter, a study by the company revealed.

Twitter analysed the top 10 emoji used for TV-related tweets between April 2014 and July 2015.

This emoji was used in 24 percent of tweets that included emojis. The laughing face was followed by the heart eyes (12 percent), crying face (8 percent) and prayer hands (6 percent), the study found.

"Since emoji characters began displaying on Twitter in April 2014, they have become a practical and fun way to convey extra meaning and emotion in the space of 140 characters," Twitter's Senior Data Specialist Joe Cruse wrote in a blog post.

"In particular, we have seen emojis used regularly in Tweets about TV, where fans can discuss what's happening, how they feel about what they're watching, or add context to their live-Tweeting," the blog read.

About 86 percent of emoji users are aged 24 or younger, with about 50 percent in the 18-24 age group. Also, a greater number of female users used emoji (57 percent) in their TV-related tweets as compared to males (43 percent).

But emoji are not just for fun as brands have increasingly started using emoji in their ad campaigns.

Twitter has also started monetising them through sponsored emojis. For instance, in September, Twitter created an emoji of two glass bottles clinking for Coca-Cola that appeared with the tweet #ShareACoke.

Also, Mountain Dew's Digital Brand Manager Christine Ngo was reported as saying in July that including emojis in one-to-one messaging drew more engagement.