2-3. Double consonants (Sokuon)
A double consonant in Japanese can be sounded out as a short pause or a hissing sound.
An example of a short pause would be, かこ(kako) and かっこ (kakko) The slight pause between か and こ indicates the double consonant.
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Now, compare あさり(asari) and あっさり(assari). The consonant “s” has a hissing sound which also makes it a double consonant.
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Example
slope/novelist
clam/simple
past/parenthesis
west/daily notes
sound/husband
painter/academic department
outside/gently
tinsistence/business trip
public/soap
butter/batter
Please come./Please cut it.
An incident happened./An experiment happened/was held.