Some words ending in -y change their ending when they are:
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conjugated verbs in the 3rd person singular of the simple present
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conjugated regular verbs in the simple past
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made into new words
Adding an -s to a word ending in -y is spelled:
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-ies when following a consonant
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-ys when following a vowel

Used with plural nouns and verbs conjugated in the simple present with the 3rd person singular.
Adding -ed to a word ending in -y is spelled:
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-ied when following a consonant
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-yed when following a vowel

Used with irregular verbs in the simple past.
Adding -er/-est to a word ending in -y is spelled:
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-ier/-iest when following a consonant
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-yer/-yest when following a vowel

Used with comparative and superlative adjectives.
When adding a suffix to a word ending in -y to form new words:
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Change the -y to an -i when following a consonant.
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Keep the -y when it follows a vowel.
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Always keep the -y when adding the suffix -ing: no matter if it is following a vowel or a consonant.
