Here are some examples of words which are frequently pronounced differently in fast speech.
Numbers
The word kümmend is often shortened to kend, and the letter h between two vowels is often dropped (with or without a change to the vowel sounds):
Kaeksa = kaheksa
Üeksa = üheksa
Öeksa = üheksa
Kend = kümmend
Kakskend = kakskümmend
Kolmkend = kolmkümmend
Viiskend = viiskümmend
Kaheksakend = kaheksakümmend
Üheksakend = üheksakümmend
Öeksakend = üheksakümmend
Past tense verbs
In fast speech, some sounds (frequently le, t or i) are dropped in the past tense:
Jõuds = jõudis
Leids = leidis
Murds = murdis
Mõts = mõtles
Mõtsin = mõtlesin
Ossin = ostsin
Tahsin = tahtsin
Tõssin = tõstsin
Üts = ütles
Ütsin = ütlesin
Past participles
The -nud ending can become -nd (or other sounds such as t, k) can be dropped):
Lasnud = lasknud
Old = olnud
Olnd = olnud
Osnud = ostnud
Pold = polnud
Rääkind = rääkinud
Käind = käinud
Läind = läinud
Tahnud = tahtnud
Tulnd = tulnud
Adverbs
Adverbs, especially those ending in -lt, often get shortened:
Aint = ainult
Kinlasti = kindlasti
Lissalt = lihtsalt
Lissat = lihtsalt
Prakselt = praktiliselt
Tõenäst = tõenäoliselt
Tegelt = tegelikult
Ea and ää
Ea can become ää (this is also a common change in the southern dialects, and, for some words, acceptable even in written language). Ae and äe also sometimes change to ää, and in fast speech sometimes e sounds like ä:
Hää = hea
Kääs = käes
Lähäb = läheb
Nääd = näed
Präägu = praegu
Pää = pea
Pääl = peal
Pääv = päev
Sääl = seal
Vähä = vähe
Diphthongs
Some other diphthongs are changed into single (long or short) vowels; usually this means that the second vowel sound disappears:
Sel = seal
Pel = peal
Peb = peab
Lääb = läheb
Kääb = käib
Vä = või
Kõge = kõige
Ku = kui
Kudas = kuidas
Kudagi = kuidagi
Kule = kuule
Mudugi = muidugi
Nääteks = näiteks
Teene = teine
Öölda = öelda
Võõbolla = võib-olla
Tõõsti = tõesti
Just one sound
Some common words are shortened in fast speech so that they sound like a single sound (vowel or consonant):
a = aga
e = ei
i = ei
m = ma
n = on
Common words and phrases
Some common phrases run together as if they are a single word, and some common words are shortened:
A = aga
Maitia = ma ei tea
Mitteriti = mitte eriti
Mitterilist = mitte erilist
Nongi = nii ongi
Sedet = seda, et
Taegaa = head aega
Trommikust = tere hommikust
Trõhtust = tere õhtust