Palatalization: Hard and Soft Consonants and Spelling

The following consonants can be hard or soft: б- бь;  в- вь;  д- дь; з- зь; л- ль; м- мь; н- нь; п- пь; р- рь; с- сь; т- ть; ф- фь. But the soft sign (ь) is only used when no vowel follows the consonant. If a vowel follows, then the special "soft" vowel is used. So, instead of writing бьыть we write бить, and instead of льубльу, люблю.

But what about the other consonants?

Well, the velar consonants к, г, х  also have hard and soft sounds: [к]-[к'], [г]-[г'], [х]-[х']. But for historical reasons, the soft sign is not used after these letters. Instead, a mix of vowels is written instead:

• к, г, х  can never be followed by ы;
• к, г, х  are not usually followed by vowels я, ё, ю, and э (note: э not е, which is used)
• such combinations can be seen in foreign words like Гётте, Хэллоуин, Гюнтер, Кэтлин.

The other six consonants are unpaired. Three are always hard - ж, ш, ц (they have no soft counterparts) - and three are always soft - ч, щ, й (these consonants have no hard counterparts). For these unpaired consonants the choice of vowel is usually determined by special spelling rules (see here for more on spelling rules)

1. After the consonants ж, ш, ч, щ the letter и is used (never ы). After the hard ones (ж ш), the sound is ы.
жить to live 
машина car 
чипсы chips 
защита protection 

2. After the unpaired soft consonants ч, щ the letters а, у are used (never я, ю in spite of the fact that the consonants are soft).
час an hour
чудо miracle 
роща grove 
ищу I'm looking for

3. After the unpaired hard consonant ц the letter ы is used in the ending of a word, the letter и is used in the root.
огурцы  cucumbers
немцы Germans
цифра number 
цирк circus

4. Й is a special case. Vowels are never written after it; instead it combines with the vowel to produce the "soft vowel": йа = я, йэ = е, йо = ë, йу = ю and йы = и