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These 10 Twitter hashtags changed the way we talk about social issues

(J.J. Alcantara/The Washington Post; iStock)

During the past decade, Twitter rendered the "pound sign" obsolete and made the "hashtag" part of our vernacular. The hashtag's uses range from sarcasm and trolling to awareness of social causes. The latter usage has been instrumental in the transition of movements from online to the real world. In honor of Twitter's 1oth birthday, here are the 10 most influential hashtags around social causes, ranked by the number of times they've been used since their inception. All numbers have been provided by Twitter.

10. #GivingTuesday

In an attempt to counteract the rampant consumerism that blankets the holiday season starting with Black Friday, Small Business Saturday and Cyber Monday (but certainly not ending there), 92Y and the U.N. Foundation gave life to #GivingTuesday. The social initiative, which began in 2012 and whose hashtag has since amassed 3,100,000 uses, asked that charities use #GivingTuesday in their call-outs for donations on the first Tuesday in December.

The first #GivingTuesday generated $10.1 million in donations.

9. #YesAllWomen

In response to Elliot Rodger's misogyny-fueled killing rampage at the University of California in Santa Barbara and the #NotAllMen defense that followed, #YesAllWomen aimed to give women a place to share their experiences with rape, abuse, sexism and judgment. The hashtag was used 3,700,000 times to help share the compelling and heartbreaking stories of women all over the world.

8. #PrayforJapan

#PrayforJapan originated after an 8.9-magnitude earthquake and tsunami hit Japan in March 2011, killing nearly 2,000 people. The hashtag, which has been used 4,000,000 times, resurfaced in November 2015 after a smaller earthquake triggered false reports of an impending tsunami. Even Justin Bieber tweeted it alongside #PrayforParis.

7. #BringBackOurGirls 

The #BringBackOurGirls hashtag miraculously managed to become a divisive one, despite its goal of uniting users around the demand for the safe return of Nigerian school girls kidnapped by a militant Islamist group. Although critics were quick to point out the "laziness" of this use of hashtag activism, some of the 6,100,000 users of #BringBackOurGirls defended the trending topic, offering their own criticism of those who shame others for not meeting their standards of awareness.

6. #IceBucketChallenge

6,200,000 uses of #IceBucketChallenge on Twitter helped make this awareness campaign so incredibly popular that folks were looking for ways to avoid it entirely. In the summer of 2014, you couldn't log on to Twitter, and even Facebook or Instagram, without seeing a friend or colleague being doused with cold water in the name of amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease) and hoping you weren't called upon to complete the challenge next.

Despite the copious cynicism the challenge inspired, the ALS Association raised millions thanks to the campaign.

5. #Sandy

In late 2012, Hurricane Sandy hit the East Coast, wreaking havoc throughout the Northeast. #Sandy chronicled the perils of those affected and the damage done in states such as New York and New Jersey. But nearly four years later, a new study suggests that the hashtag was good for more than spreading awareness.

According to a study published earlier this month in the journal Science Advances, the 7,200,000 uses of #Sandy on Twitter and other relevant location-tagged tweets helped researchers find "a strong relationship between proximity to Sandy’s path and hurricane-related social media activity." Their findings allowed the researchers to suggest that activity on social platforms, such as Twitter, can be used to rapidly assess damage and aid in disaster response.

4. #IndyRef

The Scottish independence referendum, or #IndyRef for short, monopolized much of the Twitter conversation on the evening of Sept. 18, 2014. But Twitter users weren't just following #IndyRef to learn the results of the historic vote about Scotland's leaving the United Kingdom. The hashtag was used 8,500,000 times and was a clear indicator of how political engagement and debate are occurring more frequently online.

3. #BlackLivesMatter

For those eager to criticize hashtag activism, the Internet raises you #BlackLivesMatter. Used 12,000,000 times, the hashtag has quite literally transformed from an online-community unifier to a political movement and tangible organization.

2. #LoveWins

After the Supreme Court's historic ruling on same-sex marriage, Twitter included a rainbow heart emoji with each of the 12,800,000 mentions of #LoveWins. The monumental decision led other social networks to create ways to let users colorfully show their support, such as Snapchat's custom rainbow location-based filters and Facebook's rainbow profile-picture filter.

1. #Ferguson

It should come as little surprise that #Ferguson cruised to No. 1, more than doubling the usage of the second-most popular social-issues hashtag. Since its first use, #Ferguson has been tweeted  27,200,000 times and has helped amplify the voices of a community that feared it would not be heard. Unrest in Ferguson, Mo., hit Americans' Twitter timelines before the story seized cable news's attention. Social media became a critical component of balanced coverage of the protests in Ferguson.